The below are the movies I'll be using for inspiration

Dog Soldiers
Kelly's Heroes
The Guns of Navarone
The Dirty Dozen
The Thin Red Line
Tigerland
Platoon
Bravo Two Zero
Full Metal Jacket

The Lighthorsemen
'Breaker' Morant 
Gallipoli 
Kokoda 
The Charge of the Light Brigade

Memphis Belle 
Hornblower
U-571

Red Dawn
Tomorrow, When the War Began

While not the greatest movie ever made Battle: Los Angeles would make a pretty good source of inspiration for a game where the PCs squad is having to face down an invading force of relatively unknown xenos.

Just don't get it confused with Battle FOR Los Angeles which is incredibly horrible. Especially when you realize that one of their "Weapons" is just a nerf gun they spraypainted chrome.

 Starship Troopers!!!   

Military force send to other planet to fight aliens (Tyranids)

Though I wouldn't exactly call them movies…

I am going to be using the general military activites of the "White Base" from the "Mobile Suit Gundam" anime as the general guide for the encounters of my group's regiment. Except there won't be any giant robots with angsty teenage boys piloting them, maybe a few titans in the major battles though.

3 major battles, several stealth/recon/sabotage missions, decoy missions, base defense, escort missions, amushes, etc.

Everything you could want in a major war.

A bridge too far, showing how planetary assaults and aerial assaults can be a tricky business (though I think by imperial terms that would have been regarded as a victory!)

Zulu: Showing how dicipline and a bayonet with some guts behind it can sometimes overcome terrible odds!

Zulu Dawn: Showing how dicipline and a bayonet with some guts behind are useless when you run out of ammo and your officers are idiots….

Longest day: again another good one showing the dangers of planetary assaults and how to perform a largely successful one or if you were going to incorperate sea landings

Dieppe: I'm pretty sure there was a film made about Dieppe of this name in the 1960's in the uk and if memory serves it was pretty good, I'm sure the canadians have made a newer more impressive version since, a good one to look at as if you can find it simply because it has what happens when it all goes wrong.

Oh What a Loverly War: actually the most impressive film I've seen about WW1, it gives you a really good feel of what being a soldier would have been like (i.e. horrifying) and who doesn't like a musical!  Mostly based on real events albeit with a spin on them to make them more surreal (and yes I mean that, WW1 was a weird war by anyones standard!).

Enemy at the gates: I feel more the experience of hastily raised PDF troopers in response to a chaos invasion myself then guardsmen but how you interpret it is up to you of course.

Land and Freedom: an excelent film about the Spanish Civil War, to me it suggests an interesting campaign where people play as a scratch company fighting rebels mainly consisting of the local PDF.  The imperium could be represented by the soviet union (as there are bits in the fluff where they drip feed what they regard as doomed and unimportant planets equipment in part to allow them to get anything of value out (like the soviet union did with the spanish gold)) also the way they send advisors and so on would work.  Or it could be regarded as an internal matter (which the imperium often doesn't care about, worlds in the 40k universe can often have long running wars with no one being a rebel against the imperium…….) and so the imperial navy is just cordening off the planet with maybe a rogue trader trading with both sides, selling the loyalists equipment at exorbitant prices to get any resources he can out of them while giving equipment to the rebels as if they win he gets beneficial trade rights?  http://video.google.com/videoplay?docid=-5904180592045722602 in its entirety

I have a few movies and some documentaries set in Afghanistan:

A very underrated movie imho that needs more mentioning is Pork Chop Hill (www.youtube.com/watch - Not the best quality but a good scene nonetheless).

The Thin Red Line - I'm very surprised this was not mentioned yet. www.youtube.com/watch. A great movie I think most should see.

We Were Soldiers Once and Young - Another great Vietnam movie not mentioned. www.youtube.com/watch, www.youtube.com/watch

The Battle for Marjah - The whole HBO documentary can be found on Youtube. Follows a US Marine rifle company deployed behind enemy lines - www.youtube.com/watch

There is also the Ross Kemp series about his time in Afghanistan with British soldiers - www.youtube.com/watch

Not to mention all of the combat footage posted on youtube about the fighting in Afghanistan.

British troops involved in a dawn assault on Taliban positions (2 parts) - Part 1 www.youtube.com/watch and part 2 www.youtube.com/watch

Zakalwe said:

Enemy at the Gates. I would us as an intro for the characters they are pushed forward in the assault a las gun and 2 las packs for every two people the bit. The Commissar (NPC or PC) at there back with a heavy weapons team(or squad) with heavy bolters or autocannons. After the others have moved on the Commissar gets flanked. Dooring the coerce of the battle they all meet up and complete the final objective together. Earning the respect of the commissar, and securing there friendship for the foreseeable future. The next battle is some time in the future and they have all the gear they shuld start with.

 
With the Battle for Hoth I see the PCs as Imperial soldiers cuz that's what they are. But with a little change to the script they could be defending a research base from the forces of chaos.
 

I'm a big fan of "Kelly's Heroes" (I can still remember, as a child, the scene of the panzer's turret, and I looking in awe), so I'm designing a light-hearted adventure inspired by the movie: "CALLIDUS' HEROES"! :-) I'm writing the details right now… :-D And yes, it will NOT BE canon. But I can'r resist the marvelous silliness of "going to steal the gold of the chaotics", and the moving image of young privates frenetically chipping off the chaos star from the gold ingots. It's an idea so stupid I find it irresistible.

Ciaps!

What about Mutant Chronicles, a special team of Imperial guard fights against Mutants