Codename Eagle? Doubtful, but you're running out of options at this point.

https://www.youtube.com/watch?v=amIaFm7TJ48

yeah its not that either

i may be looking in the wrong genre, instead of it being about WW1 on earth it might be a sci fi game about a WW1-style conflict on a new planet or in a regressed society or whatever. i appreciate all the suggestions but its just not any of these games, unfortunately. I had a play on Iron Storm yesterday just to be sure, since it was in my Steam library already, and its definitely not that.

Sure that it was WW1 and not WW2?

Here is a full list of all WW1 games until 2016. I took it from a study, so the info should be reliable.

List of Analysed World-War-I Games (58)

Flying (19)

Atari. (1980). Red Baron [Xbox 360]. Sunnyvale, CA: Atari.

BMB Compuscience. (1984). Sopwith [PC]. Milton: BMB Compuscience.

Cinemaware. (1990). Wings [Amiga]. Burlingame: Cinemaware.

Dynamix. (1997). Red Baron II [PC]. Fresno, CA: Sierra.

Dynamix. (1998). Red Baron 3D [PC]. Fresno, CA: Sierra.

Malibu Interactive. (1993). Blazing Skies [SNES]. Tokyo: Namco.

MicroProse. (1990). Knights of the Sky [Amiga]. Hunt Valley: MicroProse.

Namco. (1985). Sky Kid [NES]. Tokyo: Namco.

Neoqb, 777 Studios. (2009). Rise of Flight: The First Great Air War [PC]. Büren: Aerosoft.

Old Brown Dog Software. (2013). Wings: Over Flanders Fields [PC]. N.p.: Old Brown Dog Software.

Origin Systems. (1994). Wings of Glory [x86]. Redwood: Electronic Arts.

Rowan Software. (1996). Flying Corps [PC]. London: Empire Interactive.

Rowan Software. (1994). Dawn Patrol [Amiga]. London: Empire Interactive.

Silver Wish Games. (2004). Wings of War [Xbox]. Austin: Gathering of Developers.

Smart Bomb Interactive. (2010). Snoopy Flying Ace [Xbox 360]. Redmond: Microsoft Studios.

Smart Bomb Interactive. (2006). Snoopy vs. the Red Baron [PS2]. Shinagawa: Namco Bandai Games America.

subLOGIC. (1982). Microsoft Flight Simulator [PC]. Redmond: Microsoft Game Studios.

Synapse Software. (1983). Blue Max [Commodore 64]. Richmond: Synapse Software.

Third Wire Productions. (2006). First Eagles: The Great War 1918 [PS2]. London: G2 Games.


Naval (4)

Divide By Zero. (1996). Great Naval Battles V: Demise of the Dreadnoughts; 1914--18 [PC]. Mountain View: Strategic Simulations.

Rondomedia. (2007). 1914 Shells of Fury [PC]. Montreal: Strategy First.

Storm Eagle Studios. (2008). Jutland [PC]. Free Union: Storm Eagle Studios.

Turcan Research Systems Limited. (1992). Dreadnoughts [DOS]. N.p.:Turcan Research Systems Limited.


RTS (3)

GameTek. (1995). The War College: Universal Military Simulation 3 [DOS]. Davenport: Intergalactic Development.

Lesta Studio. (2008). Aggression: Reign Over Europe [PC]. Moscow: Buka Entertainment.

Lesta Studio. (2004). The Entente: Battlefields of World War I [PC]. Moscow: Buka Entertainment.

Grand Strategy (10)

Adanac Command Studies. (2007). Guns of August: 1914--1918 [PC]. Epsom: Matrix Games.

AGEOD. (2008). World War One [PC]. Gütersloh: Ascaron Entertainment.

BevelStone Production. (1995). Fields of Battle [PC]. Aarhus: BevelStone Production.

Darkest Hour Team. (2011). Darkest Hour: A Hearts of Iron Game [PC]. Stockholm: Paradox Interactive.

The Lordz Game Studio. (2012). Commander: The Great War [PC]. Luxembourg: The Lordz Game Studio.

Muzzy Lane. (2015). Making History: The Great War [PC]. Newsburyport: Muzzy Lane.

Paradox Development Studio. (2010). Victoria II [PC]. Stockholm: Paradox Interactive.

Paradox Interactive. (2006). Victoria: Revolutions [PC]. Stockholm: Paradox Interactive.

Paradox Interactive. (2005). Diplomacy [PC]. Stockholm: Paradox Interactive.

Paradox Development Studio. (2003). Victoria: Empire Under the Sun [PC]. Stockholm: Paradox Interactive.


Turn Based Strategy (4)

Blue Byte Software. (1992). History Line: 1914--1918 [Amiga]. Mountain View: Strategic Simulations.

Damon, R. (1994). Wargame Construction Set II: Tanks! [Amiga]. Mountain View: Strategic Simulations.

Frog City Software. (1996). Imperialism [PC]. Mountain View: Strategic Simulations.

Red Wasp Design. (2012). Call of Cthulhu: The Wasted Land [PC]. Bristol: Red Wasp Design.


FPS (9)

8monkey Labs. (2009). Darkest of Days [PC]. Cedar Falls: Phantom EFX.

Gallica Game Studio. (2013). The Trench: 1916 [PC]. Seine et Marne: Gallica Game Studio.

Kriegsgraben und Stormvogel. (2011). 1916: Der Unbekannte Krieg [PC]. Aalborg: Kriegsgraben und Stormvogel.

M2H and BlackMill Games. (2013). Verdun [PC]. Alkmaar: M2H and BlackMill Games.

Refraction Games. (1999). Codename Eagle [PC]. New York: Take-Two Interactive.

Starbreeze Studios. (2007). The Darkness [PC]. Novato: 2K Games.

The Farm 51. (2010). Necrovision: Lost Company [PC]. Austin: Aspyr Media.

The Farm 51. (2009). Necrovision [PC]. Austin: Aspyr Media.

TopHat Game Studios. (2012). The Somme: Lest We Forget [PC]. Cary: Epic Games.

Towerdefence/Castle Attack (3)

ConArtist. (2008). Warfare 1917 [PC]. Irvine: Armor Games.

Gameslab, BBC Scotland New Media. (n.d.). Trench Warfare. In BBC Schools (Ed.), Curriculum Bites World War One [PC]. Salford: BBC. Retrieved on March 29, 2014: http://www.bbc.co.uk/schools/worldwarone/hq/trenchwarfare.shtml.

Signal Studios. (2012). Toy Soldiers [PC]. Redmond: Microsoft Game Studios.


Miscellaneous (6)

Bay 12 Games. (2004). WWI Medic [PC]. Silverdale: Bay 12 Games.

Infogrames Entertainment, SA. (2000). Hogs of War [PC]. Paris: Infogrames Entertainment, SA.

Porter, D. & Williams, H. (2014). Trench Mission. In The National Archives (Ed.), Trench Experience [PC]. London: The National Archives. Retrieved on March 29, 2014: http://www.nationalarchives.gov.uk/education/greatwar/g3/game/.

Retro Army. (2013). Super Trench Attack [PC]. Edinburgh: Retro Army.

Smoking Cars Productions. (1997). The Last Express [PC]. Beverly Hills: Interplay Entertainment.

Ubisoft Montpellier. (2014). Valiant Hearts: The Great War [PC]. Montreuil: Ubisoft.

Also you could check out this list:

[url=https://en.wikipedia.org/wiki/Category:Alternate_history_video_games]https://en.wikipedia.org/wiki/Category:Alternate_history_video_games[/url]

Maybe Necrovision, also Clive Barker's Undying features a WW1 narative but isn't used in actual gameplay afaik.

Mortyr maybe?

https://www.youtube.com/watch?v=0gGn7GN2ztc

You can't remember anything about the actual gameplay? Like, specific mechanics: Was it a cover-based shooter, or more run-&-gun? Did it have regenerating health, health packs, little bit of both, something else? Did it have a weapon limit, or could you pick up and carry every weapon without having to drop any? For that matter, were there any distinctive weapons you can recall? How about the save system -- autosave checkpoints, manual saves, both? Were there vehicles you could drive?
Any other little details you can remember about the gameplay, story, visuals, etc., could only help.

bear in mind that this was 15 years ago, but the only weapons i remember were guns. no vehicles that i remember. as far as i remember there were no dropped weapons and you could hold however many you wanted

i dont know about the rest of it. as i said, the intro is really the main thing that stuck with me