Verdun

Verdun is the first multiplayer FPS set in a realistic First World War setting. The merciless trench warfare offers a unique battlefield experience, immersing you and your squad into intense battles of attack and defense. 
The game takes place on the western front between 1914 and 1918, in one of the bloodiest conflicts in world history. The developers were inspired by the infamous Battle of Verdun France in 1916, The game includes many historically accurate features such as realistic WW1 weaponry, authentic uniforms and maps based on the real battlefields of France and Belgium. 

The Frontlines game mode is unique in its tactical complexity. The realistic trenches are challenging to fight in and require tactical cunning to capture and defend. The Entente and Central Powers strive to gain control of frontline sectors. In one battle you're rushing the enemy trenches in an offensive battle in order to gain ground, In another battle you might be defending your recently conquered ground against an enemy counter-attack. 

Features:

• Realistic World War 1 gameplay: Authentic weaponry with realistic bullet physics, skill based weapon handling, poisonous gas with a claustrophobic gas mask experience and artillery barrages
• Tactical squad-based FPS: Unique squad leveling system, distinct squad types and roles, voice chat
• True trench warfare: Real-time dynamic frontline with momentum-based attack and counter-attack gameplay
• Authentic World War 1 setting: Typical WW1 music and style, historical battlefields set on the Western Front 
• Challenging game modes: Team-based Frontline and skill-based Rifle Deathmatch

Reviews:

“I became immersed in its careful pacing and focus on squad movement.” 
Gamespot - Cameron Woolsey 

“Verdun's given me an excellent understanding of what a mess World War I was. Verdun's Frontlines mode really is sort of ingenious—and I think this is definitely one worth checking out, especially if you're already interested in the subject matter.” 
PCWorld - Hayden Dingman