I can only speak to what some refer to as the "Western Front" i.e. the Franco-Belgian lines. As with all things entertainment, the movie has granules of truth. Yes, nighttime scouting missions into No Man's Land were undertaken by most combatant forces to ascertain trench depth, troop strength, and, in some cases, troop retrieval. These missions took place with extreme stealth and a variety of weapons. Melee weapons such as clubs, hatchets, and sharpened entrancing tools were common place, and there is even evidence of spears being used in assaults and counterattacks. German forces, as well as some Allied units, utilized body armor for scouting missions as well. In fact, there were entire German squads, called 'Sturmtruppen' outfitted with melee weapons, and in some cases body armor, that carried out nighttime missions and specialized terrorising trench attacks thoughtout the Western Front. Granted, the movie takes liberties with this--- the idea of night scouting missions carried out while wearing gas masks is ludicrous. And hand to hand skirmishes were, according to eyewitnesses, desperate close quarter brawls. No time for fancy blade use or flipping about as the movie shows. As for the firing at the least sound or a single gunshot--- there are accounts that mention these things happening in both first hand accounts as well as secondary sources.

There are several books that mention this, especially war diaries and secondary sources. Here are a few:

Keegan, John-- The First World War

Murray, Nicholas. The Rocky Road to the Great War: The Evolution of Trench Warfare to 1914.

Ellis, John. Eye-Deep in Hell – Life in the Trenches 1914–1918

Johnson, Thomas M., and Fletcher Pratt. The Lost Battalion

Gudmundsson, Bruce I. Stormtroop Tactics: Innovation in the German Army, 1914-1918

Lengel, Edward. To Conquer Hell: The Meuse-Argonne, 1918.

Sheldon, J. The German Army on the Somme: 1914–1916.

Yockelson, Mitchell. Forty-Seven Days: How Pershing's Warriors Came of Age to Defeat at the German Army in World War I

I wholeheartedly recommend Gudmundsson and Ellis.

Forgive any grammatical errors, as this was written on a mobile.