Forum adverts like this one are shown to any user who is not logged in. Join us by filling out a tiny 3 field form and you will get your own, free, dakka user account which gives a good range of benefits to you: No adverts like this in the forums anymore. Times and dates in your local timezone. Full tracking of what you have read so you can skip to your first unread post, easily see what has changed since you last logged in, and easily see what is new at a glance. Email notifications for threads you want to watch closely. Being a part of the oldest wargaming community on the net. If you are already a member then feel free to login now.

From memory boarding actions in BFG cause critical hits, which are not necessarily going to destroy the ship, but significantly degrade is capabilities.

Terminators don't need to slaughter their way to the bridge, as they would just teleport to the bridge. Otherwise, raiding style actions would be targetted on something important that you can hit and then retreat from, leaving the actual destruction of the ship to your ships primary weapons.

Otherwise, if the assault is not just a raid, but an attempt to entirely depopulate the ship, a concerted boarding action is effectively like an amphibious assault. Secure a bridgehead that can enable supplies to be brought in.

BFG has 2 types:

1. Hit and Run attacks:

These are the attacks caused by boarding torpedoes and attack craft like Thunderhawks, each delivering roughly a squad of Marines with the aim of targeting important systems to knock out. In game effects these caused critical hits, which though repairable, might have enough effect to affect the larger picture. An example might be destroying an important power coupling, cutting off power to all the weapons along one side of the enemy ship. Suddenly any friendly ships along that side are unopposed for at least the time it takes to repair that critical hit (which is often more about re-routing power rather than outright repairing the destroyed location).

2. Boarding actions:

These are actual close range (for BFG scale anyway) boarding actions between ships. Ships with larger crews (i.e. higher Damage) do better though SM have a bonus to the overall total, and their Damage points represent a smaller number of actual bodies (reflecting how SM and their serfs do better than standard naval armsmen of the Imperial Navy or Chaos cultists/slave crew). This can cause far more destruction, leading to more Damage and more (plus more severe) critical hits, that can lead to an effective ship kill.

Could people just try not to counter argue an obvious hyperbole.

Sure Astartes "do" in lore all the things they are framed to do... its just like supermodels in RL... they are indeed gorgeous people... the photographer and his team... the magazine staff... the hair dressers... the difgital editors... the marketing team... etc have nothing to do with how the costumer perceives the supermodel.

Incomming counter argument that Astartes are fiction incoming in 3, 2, 1...

Vatsetis wrote:
Thanks for confirming by POV.... dear Eldenfirefly

If a single squad of termies was sent into a boarding action against a battleship they would be out of ammo for their bolter and heavy weapons and their CC weapons will be depleted/broken/useless at half the way ... even if the only thing the OPFOR crew/chaff did was sitting quietly and in order in the wide corridors of their battleship waiting for execution.

Perhaps with enough resupplies (from the chapter serfs and servitors) the termies might be able to slaugther the way into the bridge after a week.

Meanwhile, the "non astartes" elements of the chapter perhaps have been able to defeat altogether the OPFOR fleet... obviously all the honour and attetion will be won by the Termies.

Yep, thats how idiotic loyalist SM are in the setting because GW dont want to multiply their numbers in a significant manner for esoteric reason.

There are tons of lore about how space marines or terminators slaughter their way to the bridge or the engines of a ship. Heck, the final battle of the Horus Heresy was about the Emperor teleporting to Horus's flagship. What is this "running out of ammo" you are talking about. lol Don't you know, space marines bolters have infinite ammo? lol.

On a more logical front. Terminators don't even need to use their bolters. They will just let whatever puny gun the ship crew have ping off their terminator armor and lumber up and smash the ship crew to bits. You think the ship crew have cannons and tanks hidden within their bunkheads and gang ways ? Why even bother with bolters in the small confines of a ship. Just smash everything to bits with power fists and lightning claws.

CC weapons are built to be hardy and last. I don't think they will so easily break from just one boarding action. Especially not when they are used to smash aside frail guardsmen bodies. A power fist or a lightning claw isn't just the hardest substance known to the imperium, it also has an energy field around it. One that violently disrupts any solid matter it touches. Terminators can literally smash their own way through the walls and bulkheads of a ship. They don't even need to follow its corridors.

A squad of terminators can smash their way through a battleship's crew to the Engines or Bridge easily. Literally nothing will stop them unless you have your own marines or terminators onboard.

A boarding action on a starship has so many targets that are vital to basic operation that even taking one or two offline will render the ship useless.
Take out life support and nobody breathes, engines and the ship can't move, comms and it can't call for help. If any of these go down it's simply a matter of time before the invaders win.

If you look at the Vigilus lore. Magnus Calgar had prepared a huge fleet to defend Vigilus. Then Abaddon opened demon portals on the ship bridges and demons directly assaulted the bridge crew. The fleet retreated in disarray back to Vigilus amidst heavy casualties. Boarding actions on ships, be it by teleportation, boarding torpedoes or opening portals directly on the bridges are part of the lore in 40k. And they are very often very effective.

Regarding the last few posts... Thats exactly how I felt when playing with my termie squads in Space Hulk.



Automatically Appended Next Post:

Eldenfirefly wrote:
If you look at the Vigilus lore. Magnus Calgar had prepared a huge fleet to defend Vigilus. Then Abaddon opened demon portals on the ship bridges and demons directly assaulted the bridge crew. The fleet retreated in disarray back to Vigilus amidst heavy casualties. Boarding actions on ships, be it by teleportation, boarding torpedoes or opening portals directly on the bridges are part of the lore in 40k. And they are very often very effective.

Nice to see that 40k has reach the level of teleportation silliness of Star Trek.

You are talking about a 40k setting that has massive greater demons, xenos races and super humans, and the setting has psychic warp powers, xenos tech and thousand of year old tech. Basically, silliness is the default here.

It is kinda cool though. Else we won't be playing wahammer 40k or discussing it here wouldn't we ?

I don't think you have to shoot everyone, you just need get to bridge/engineering etc. and the ship is yours. Or if its a smash and grab get as close to the bridge as possible, wander in, destroy everything, leave, ship out of fight.


Automatically Appended Next Post:

Iracundus wrote:
There is also the bit from Andy Chambers that I posted earlier saying Imperial ships also have additional space to transport ground troops from 1/3 to 1/2 their total crew size.

I believe the background was a standard cruiser can transport 1 regiment. Infantry wise I think the finger in the air for this was 6000 men.


Automatically Appended Next Post:

mrFickle wrote:

However I do prefer the idea of space marine chapter having lots of serf running around keeping everything going while still the space marines arrogantly aren’t aware of what they are contributing

I think their fluff is pretty consist with ignoring the people who run their ships, often being born and dying upon them!

 Gert wrote:
A boarding action on a starship has so many targets that are vital to basic operation that even taking one or two offline will render the ship useless.
Take out life support and nobody breathes, engines and the ship can't move, comms and it can't call for help. If any of these go down it's simply a matter of time before the invaders win.

I agree entirely, but the thought occurred that 40k ships are so unutterably vast that life support might not be a quick win target

There is probably an in depth study that could be done as to how long the oxygen supply would last without any renewal based on volume versus different crew estimates and impact of ship fires. And also how long it would take for the heat to leach out of something that massive. But I'm not doing it

 Flinty wrote:

 Gert wrote:
A boarding action on a starship has so many targets that are vital to basic operation that even taking one or two offline will render the ship useless.
Take out life support and nobody breathes, engines and the ship can't move, comms and it can't call for help. If any of these go down it's simply a matter of time before the invaders win.

I agree entirely, but the thought occurred that 40k ships are so unutterably vast that life support might not be a quick win target

There is probably an in depth study that could be done as to how long the oxygen supply would last without any renewal based on volume versus different crew estimates and impact of ship fires. And also how long it would take for the heat to leach out of something that massive. But I'm not doing it

Actually in BFG, only a few critical hits are not repairable. Capital ships in 40K generally have so many redundancies and alternative power pathways that it is difficult to truly permanently shut down some function with targeted pinpoint hit and run attacks.

Smaller escort ships are a different matter, though in terms of balance I believe Andy Chambers actually stated somewhere that he regretted it, as Hit and Runs became a easy way to destroy escorts.

 Flinty wrote:

 Gert wrote:
A boarding action on a starship has so many targets that are vital to basic operation that even taking one or two offline will render the ship useless.
Take out life support and nobody breathes, engines and the ship can't move, comms and it can't call for help. If any of these go down it's simply a matter of time before the invaders win.

I agree entirely, but the thought occurred that 40k ships are so unutterably vast that life support might not be a quick win target

There is probably an in depth study that could be done as to how long the oxygen supply would last without any renewal based on volume versus different crew estimates and impact of ship fires. And also how long it would take for the heat to leach out of something that massive. But I'm not doing it

It’s 40k, so the answer is “how long does the plot require” or “what sounds cool”

But scale is a big thing here. Giant stupid cathedral ceilings do make for a big air reserve, even if the room is sealed off. A a km long ship is going to take a LOT of time to radiate heat and cool off.

Eldenfirefly wrote:
Because the favored action taken by many chaos factions and Space Marines as well is boarding. And because one squad of terminators successfully boarding a battleship means that battleship is dead because nothing on it can stand up against a single squad of terminators. It might take them a while to slaughter their way to the bridge, but they will eventually get there.

Mere mortals are no match for hulking space marines in the close confines of a spaceship. Space Marines will walk through them like chaff, and this would apply doubly for Terminators.

I disagree. Any warship worth its salt would be prepared: it will have blast doors (they won't stop the boarding party forever but they will slow it down), an armory full of short-ranged but high-penetration weapons such as melta guns, etc. Not to mention that time is always of the essence in war. If the Termies take an hour to butcher and breach their way to the bridge, by the time they get there, their whole reason for boarding the ship may be moot. For example, the ship may already have won the space battle with the strength of its guns.

The problem with some "Marines are unbeatable by non-Marines" arguments is that they use simple, small-scale scenarios (yay alliteration) to extrapolate on a much vaster and more complex scale, and without accounting for tactics, logistics, the element of surprise, common sense, self-preservation, and that annoying little wrinkle called "one guy can't be everywhere at once or dodge every attack coming his way".

Just because a Marine could win 100 consecutive duels against individual guardsmen without a scratch in his armor doesn't make him a match for 100 guardsmen in any kind of realistic situation.

.

-Guardsman- wrote:

Eldenfirefly wrote:
Because the favored action taken by many chaos factions and Space Marines as well is boarding. And because one squad of terminators successfully boarding a battleship means that battleship is dead because nothing on it can stand up against a single squad of terminators. It might take them a while to slaughter their way to the bridge, but they will eventually get there.

Mere mortals are no match for hulking space marines in the close confines of a spaceship. Space Marines will walk through them like chaff, and this would apply doubly for Terminators.

I disagree. Any warship worth its salt would be prepared: it will have blast doors (they won't stop the boarding party forever but they will slow it down), an armory full of short-ranged but high-penetration weapons such as melta guns, etc. Not to mention that time is always of the essence in war. If the Termies take an hour to butcher and breach their way to the bridge, by the time they get there, their whole reason for boarding the ship may be moot. For example, the ship may already have won the space battle with the strength of its guns.

The problem with some "Marines are unbeatable by non-Marines" arguments is that they use simple, small-scale scenarios (yay alliteration) to extrapolate on a much vaster and more complex scale, and without accounting for tactics, logistics, the element of surprise, common sense, self-preservation, and that annoying little wrinkle called "one guy can't be everywhere at once or dodge every attack coming his way".

Just because a Marine could win 100 consecutive duels against individual guardsmen without a scratch in his armor doesn't make him a match for 100 guardsmen in any kind of realistic situation.

.

... you wanna fire off a armor piericing melta gun on a small metal box floating in the void of space?

yeaaaaaah that might not go very well. and yeah if you drop termies off a kilometer away from the bridge they may not board it in time but chances are they're a lot closer.

Useally when a ship is boarded by marines in the fiction what you see is squads deploying throughout the ship and aiming at various key parts (the bridge and the engine room specificly)

often the Marine ship will come in, lay it's payload and then move out at speed. letting the deployed marines finish ship off while it sits out of range

The external hull of warships are intended to protect against starship grade weapons. I doubt that any infantry portable weapon has any chance of breaching the hull. The Cain books even talk about simple shuttles being able to shrug off lascannon fire as they are hardened for reentry.

Vatsetis wrote:
Thanks for confirming by POV.... dear Eldenfirefly

If a single squad of termies was sent into a boarding action against a battleship they would be out of ammo for their bolter and heavy weapons and their CC weapons will be depleted/broken/useless at half the way ... even if the only thing the OPFOR crew/chaff did was sitting quietly and in order in the wide corridors of their battleship waiting for execution.

Perhaps with enough resupplies (from the chapter serfs and servitors) the termies might be able to slaugther the way into the bridge after a week.

Meanwhile, the "non astartes" elements of the chapter perhaps have been able to defeat altogether the OPFOR fleet... obviously all the honour and attetion will be won by the Termies.

Yep, thats how idiotic loyalist SM are in the setting because GW dont want to multiply their numbers in a significant manner for esoteric reason.

Haha…. Ammo doesn’t, ‘run out’. It just keeps coming

Also lighting claws

 Flinty wrote:
The external hull of warships are intended to protect against starship grade weapons. I doubt that any infantry portable weapon has any chance of breaching the hull. The Cain books even talk about simple shuttles being able to shrug off lascannon fire as they are hardened for reentry.

which doesn't jive with the fact that Imperial fighters are using weapons like lascanons and missile launchers, but we could spend pages discussing this issue alone

The lore is full of accounts of Terminators and normal Space Marines conducting boarding actions against enemy ships - often small squads of Terminators teleporting into vital areas of the ship with the aim of crippling it. A casual perusal of a few books on my shelf found plenty from both the Horus Heresy and the 40K setting. Occasionally the normal crew will take down a Space Marine, but often it comes to defending Space Marines/Dreadnoughts coming out of stasis to save the day (or not).

You don't have to like the lore, but that aspect has been consistent for as long as I have been following it.

If you can't stand Space Marines then 40K is going to be tough to enjoy. Sorry?

Anyhoo.

Also, we can't assume that the space navy personnel manning fleet ships are trained and equipped the way astra millitarium troops are. They are trained to operate a space ship, they are not trained to fight like the way Astra Millitarium troops are trained to.

Its like in the modern world we are in, the crew of a battleship are trained to operate said battleship. They are not trained as ground troops or marines.

Also, how many tanks, artillery, or bazookas do you think a battleship is going to be carrying on board despite having thousands of people as crew ?

I don’t think many chapter would use staff and crew provided by the imperial navy. I imagine that dark angels have serfs, crew and navigators all somehow indoctrinated into absolute loyalty to the chapter even over the imperium.

Otherwise a few downloads from data banks and someone might be trying to sell secrets on the/a black market

We do know broadly what Naval Armsmen are armed with. They are described as using things like shotguns, lasguns, and some close combat weaponry, wearing mostly flak though possibly carapace (either actual carapace or repurposed protective equipment like those boiler suit looking ones with helmets in Jes Goodwin sketches). I envision them much like Solar Auxilia in appearance.

Either way, they are roughly equivalent to IG (i.e. normal unenhanced humans). They are one on one less than the Chapter serfs who may include partially enhanced members that failed some trial on the path towards becoming a full fledged Marine. That is why SM boarding actions get +1 in BFG. However, Imperial battleships have more Damage points than a SM Strike Cruiser so could potentially still fight and win by sheer numbers (if fresh).

it's possiable some chapter serfs might have differant equipment, on the other hand some chapter serfs may be worse equipped, it entirely depends on the chapters relationship with their followers. which varies anywhere from "valued friends and comrades" to "shut up slave!"

BrianDavion wrote:
... you wanna fire off a armor piericing melta gun on a small metal box floating in the void of space?

Hence why I said short-ranged. 40k ships aren't "small metal boxes", they are vast enough for having plenty of room to shoot melta weapons without damaging the hull. And besides, if you're faced with a Terminator boarding party, you might just be desperate enough to risk causing a hull breach. Presumably the ship has numerous doors to limit the loss of air to a single section/level.

Eldenfirefly wrote:
Its like in the modern world we are in, the crew of a battleship are trained to operate said battleship. They are not trained as ground troops or marines.

That's because boarding actions don't happen in 21st-century warfare. In the Age of Sail, where boarding actions were common, ships had men who were well-trained for fighting in close confines. In a hypothetical future where boarding actions are common again, it's a safe bet that shipboard security personnel will make a return.

TangoTwoBravo wrote:
If you can't stand Space Marines then 40K is going to be tough to enjoy. Sorry?

Show me where anyone has expressed such a sentiment.

.

BrianDavion wrote:

 Flinty wrote:
The external hull of warships are intended to protect against starship grade weapons. I doubt that any infantry portable weapon has any chance of breaching the hull. The Cain books even talk about simple shuttles being able to shrug off lascannon fire as they are hardened for reentry.

which doesn't jive with the fact that Imperial fighters are using weapons like lascanons and missile launchers, but we could spend pages discussing this issue alone

Furys - the standard imperial orbital fighter - use banks of lascannons on one another, and on similar sized targets - thunderhawks, torpedoes, etc.

The shuttles from the Caine series are simple shuttles but they're virtually lascannon proof because they're company-scale dropships. Will they take damage from a lascannon? Yes. Will it meaningfully affect their capability? Not unless you've got a whole swathe of the things.

Starships are the same but more so. Fighters can cause what's basically superficial damage only with what you might consider '40k scale' guns.

Whilst scale in 40k is vague at best, to put into perspective 28mm is the size of a full-grown human. So lets say imperial soldiers are all strapping examples of humanity and it's 2 metres tall. A sword class frigate is about one and a half kilometres long by three hundred metres wide, so the 'top' of the ship, lets say is about 1000m by 100m.

by that scale, a putative "starship" board is about 22 realm of battle tiles long and 2 wide, entirely covered in bastions, void shield generators, aquila macrocannon emplacement 'gun batteries' and firestorm redoubt 'flak emplacements'. Which would be one hell of a sight!

a ship with a half-dozen lascannons can potentially destroy the odd flak emplacement, which is tactically useful, but cannot realistically hurt a target on that scale in a way that can't be fixed given a few hours. Thats why that job falls to the bombers, who turn up with stuff more like deathstrike missile warheads.
,

...and as far as using destructive weaponry in a starship is concerned....I agree. A crew will be hesitant to do so because secondary damage to their ship is an issue. Hence the primary weapons of armsmen being generally shown as flamers, shotguns, rotor cannons, etc.

However....given a choice between structural or system damage to the machine shop on E deck, and letting a terminator assault squad into the plasma drive halls.......I'm pretty sure they'd take the risk of the odd secondary explosion!

Furies have ten heavy lascannon barrels, according to FFG- probably something akin to the heavy lascannons on Firestorm redoubts or Icarus lascannons. Definitely a threat to smaller vehicles and AA weapons, but won't dent the armour of a void ship.

-Guardsman- wrote:

Eldenfirefly wrote:
Because the favored action taken by many chaos factions and Space Marines as well is boarding. And because one squad of terminators successfully boarding a battleship means that battleship is dead because nothing on it can stand up against a single squad of terminators. It might take them a while to slaughter their way to the bridge, but they will eventually get there.

Mere mortals are no match for hulking space marines in the close confines of a spaceship. Space Marines will walk through them like chaff, and this would apply doubly for Terminators.

I disagree. Any warship worth its salt would be prepared: it will have blast doors (they won't stop the boarding party forever but they will slow it down), an armory full of short-ranged but high-penetration weapons such as melta guns, etc. Not to mention that time is always of the essence in war. If the Termies take an hour to butcher and breach their way to the bridge, by the time they get there, their whole reason for boarding the ship may be moot. For example, the ship may already have won the space battle with the strength of its guns.

The problem with some "Marines are unbeatable by non-Marines" arguments is that they use simple, small-scale scenarios (yay alliteration) to extrapolate on a much vaster and more complex scale, and without accounting for tactics, logistics, the element of surprise, common sense, self-preservation, and that annoying little wrinkle called "one guy can't be everywhere at once or dodge every attack coming his way".

Just because a Marine could win 100 consecutive duels against individual guardsmen without a scratch in his armor doesn't make him a match for 100 guardsmen in any kind of realistic situation.

.

This. Terminators absolutely have an advantage against any individual squad an Imperial Navy crew can muster, but Naval warships are literal fortresses that are incredibly dangerous to board.

The entire reason Terminator armour exists is because boarding actions are so dangerous even for power-armoured Marines. The Imperial Fists excel at boarding actions because they treat voidships as fortresses and boarding actiins as sieges. A major Imperial warship will have heavily defended choke points with heavy weapon turrets and fire lanes with no cover for attackers- basically bunkers. Everything about a ship gives home-field advantage to the defenders. Another issue is that layouts may vary- key power conduits may usually be in position X on a Mars-produced Lunar-class Cruiser, but this one was repaired in Bakka following heavy damage and has them in position Y instead. Now your forces have fought to a relatively unimportant part of the ship.

Imperial Navy ships have Armsmen, who always carry weapons and act as shipboard regulation (police) as well as the main security force against boarders and the main force for boarding enemies or forming landing parties. They are generally well equipped and well trained, and probably wear armour akin to carapace armour or the Solar Auxilia equipment. They will almost certainly have void suits available for combat too. They are typical described as being equiped with shotguns or "shotcannons" or lascarbines. They are broadly analogous to marines in the age of sail, except they appear to be an organic part of the Naval organisation rather than a semi-separate organisation-within-an-organisation with army ranks. Modern Naval police have similarities too.

However, it also appears that other ratings (who normally do not get weaponry to minimise mutinies) are drilled in using weapons and are issued weapons from the lockers to help in boarding actions, again in the same vein as the age of sail. The FFG info on the Navy includes the position "Master of Arms", for example, who is responsible for drilling the ratings. So with this in mind, to board a Navy ship would involve facing a well-trained elite leading hordes of local crew members in prepared defensive positions.

Where Space Marines excel is concentrated force- in any given space, they are superior to the squad they are fighting in that corridor, one on one. It is very hard to bring numbers to bear in confined spaces, so Marines have a local advantage for the majority of the time. However, they will still suffer casualties to attrition and defensive positions, and ships are still dangerous to them. In BFG, Marines had a bonus to boarding, not an instant win button.

Nobody is saying Marines auto win boarding actions but they are significantly more likely to do so than mortal forces. A large group of Armsmen might not immediately die but they aren't going to kill a Terminator, at best they'll damage a knee joint. In return the Terminators absolutely will kill them. As for arming the regular crew, when you're just getting boarded and don't have to worry about firing the weapons, maintaining reactor safeties, keeping the engines cooled and a hundred other tasks, then yes arming the ratings is an option but no in a void battle. If you're down to arming slaves and ratings in vital sections of the ship its already too late.
And as a side note, FFG products might provide lots of info but that info has never been considered as part of canon by GW. Its the same for all licenced products. The Blood Ravens weren't canon until Deathwatch: Overkill had a Blood Raven model.

 Gert wrote:
Nobody is saying Marines auto win boarding actions but they are significantly more likely to do so than mortal forces. A large group of Armsmen might not immediately die but they aren't going to kill a Terminator, at best they'll damage a knee joint. In return the Terminators absolutely will kill them. As for arming the regular crew, when you're just getting boarded and don't have to worry about firing the weapons, maintaining reactor safeties, keeping the engines cooled and a hundred other tasks, then yes arming the ratings is an option but no in a void battle. If you're down to arming slaves and ratings in vital sections of the ship its already too late.
And as a side note, FFG products might provide lots of info but that info has never been considered as part of canon by GW. Its the same for all licenced products. The Blood Ravens weren't canon until Deathwatch: Overkill had a Blood Raven model.

Yeah, but when you have an absolute paucity of published info to go on for the Imperial Navy, the FFG stuff is generally the best we've got. In addition, many of the writers have written for GW proper too, and not a lot contradicts previous lore. Is FFG products not being canon stated officially anywhere?

That aside. Assuming your Terminators won't become casualties is how you will loose Terminators- they are not invulnerable. They will be incredibly hard to stop but there will be plenty of tools and weapons that could harm them if they become complacent- Naval crews will have access to meltaguns, lascutters, breaching charges, welders etc. Naval troopers still need to be able to conduct assaults on enemy vessels, which include armoured bulkheads and the like, and they need to be able to perform damage control on their own vessels- that all requires cutting or breaching thick plate. Ammo is a concern too- the Space Hulk game includes background about how the Terminator forces aboard are being regularly resupplied to maintain their beachhead (voidhead?) on the hulk, with a perimeter surrounding a safe zone. All of this combined means Terminators will need to be careful to avoid being damaged or even killed. Are they massively advantaged against those they face? Yes. But they are attacking into prepared defences manned by crew with heavy weaponry intended for breaching ships. A good strategy could be to use explosives to immobilise and mission-kill a Terminator by dropping them through the floor, for example.

Why do you assume arming crew members means a ship is already in dire straits? Obviously in an all-out boarding action between two vessels, all hands will be engaged, but even against hit-and-run attacks there will be surplus crew available as a back up. Ships run multiple watches to maintain 24 hour service, so in a battle stations scenario there will be excess crew to replace casualties, perform damage control, and repel boarders. In addition, a locally threatened area is going to be better off taking up weapons than just being shot whilst manning their station.

 Haighus wrote:
Yeah, but when you have an absolute paucity of published info to go on for the Imperial Navy, the FFG stuff is generally the best we've got. In addition, many of the writers have written for GW proper too, and not a lot contradicts previous lore. Is FFG products not being canon stated officially anywhere?

It's one of those things where GW says "licensed material is made with our product but isn't necessarily canon within the product". It's not stated explicitly but more of an unwritten rule that's known amongst staff. It's cool and whatever but it's not "Core GW" so it's not "verified" as such.

That aside. Assuming your Terminators won't become casualties is how you will loose Terminators- they are not invulnerable. They will be incredibly hard to stop but there will be plenty of tools and weapons that could harm them if they become complacent- Naval crews will have access to meltaguns, lascutters, breaching charges, welders etc. Naval troopers still need to be able to conduct assaults on enemy vessels, which include armoured bulkheads and the like, and they need to be able to perform damage control on their own vessels- that all requires cutting or breaching thick plate.

Using breaching weapons on your own ship is a surefire way to lose said ship. If you miss a shot with a Laslock or Shotgun you might chip the paint or dent the walls. If you miss with a Meltagun or a Breaching Charge, you've blown a hole in the ship which might allow the invaders access to other parts of the ship. That or you depressurise a compartment and your entire unit is sucked into space while the Terminators with maglocked boots laugh at you. The idea of repelling boarders is to limit damage to your vessel not do more damage. If you want to be precise with these weapons you need to get close which is something you absolutely don't want to do with a Terminator or even normal Astartes. You're not factoring transhuman dread into your argument at all here and it plays a significant role. I'm not saying Terminators are invincible because that would be wrong, I'm saying that Naval Armsmen are unlikely to come even close to fending off such an action without divine intervention playing a part. I'm not talking about BFG where Marines get a +1 to boarding actions, I'm talking about the background where it's been shown time and time again that the boarding actions Astartes excel at are 9/10 times victories against mortal forces.

Ammo is a concern too- the Space Hulk game includes background about how the Terminator forces aboard are being regularly resupplied to maintain their beachhead (voidhead?) on the hulk, with a perimeter surrounding a safe zone. All of this combined means Terminators will need to be careful to avoid being damaged or even killed. Are they massively advantaged against those they face? Yes. But they are attacking into prepared defences manned by crew with heavy weaponry intended for breaching ships. A good strategy could be to use explosives to immobilise and mission-kill a Terminator by dropping them through the floor, for example.

Space Hulk is not an accurate way of depicting a normal boarding action. A Hulk is a colossal monster comprised of ships of all types and races, debris, asteroids, starbases, and god knows what else. Mapping a Hulk is an impossible task because of this. Not only that but Hulks only have a set time in realspace before they translate back into the Warp. There are unknown and varied enemies on board from Genestealers to Chaos Space Marines. You can't teleport easily into a Hulk because of intense radiation and the aforementioned lack of interior knowledge.
A normal boarding action has none of this. You know who/what you'll be fighting with a good degree of certainty, where vital systems are, an unlikely chance of random Warp jumps and an ability to use a variety of boarding methods (teleportation, torpedoes, assault boats, etc.).

Why do you assume arming crew members means a ship is already in dire straits? Obviously in an all-out boarding action between two vessels, all hands will be engaged, but even against hit-and-run attacks there will be surplus crew available as a back up. Ships run multiple watches to maintain 24 hour service, so in a battle stations scenario there will be excess crew to replace casualties, perform damage control, and repel boarders. In addition, a locally threatened area is going to be better off taking up weapons than just being shot whilst manning their station.

Sure you could arm the galley staff or offshifters but what use are they going to be? They aren't going to be well trained or worthwhile for anything but stalling and if you do manage to drive off the boarders then you might have half your crew dead in just the attempt, which means you're pretty screwed.

Astartes don't try to "hold ground" in a ship to ship boarding action. They get in, hit their targets, and get out. As quickly as possible, before the ships defenders can properly react. In Soul Hunter, the Night Lords assault on the Sword of the God Emperor takes 30 minutes, from the time their Dreadclaws hit the ship until they left the same way they came in (well, except for 1st Claw, but that's another story). In that time they destroyed the bridge and secondary enginireerium deck, enough to cripple the ship and leave it ineffective in the ongoing space battle. Then the Traitor ships cut it to pieces. The Night Lords lost five Astartes in the attack, and that wasn't during the boarding action, it was from their Dreadclaw being destroyed on the way in. The ships defenders didn't have time to assemble an adequate defense in that short time frame, and their ship died. Remember, Astartes are shock troops.

Yep Astartes seem to be very good at dealing with unprepared crews when they have the surprise advantage....