French forces dug trenches for defense in World War I.
French forces dug trenches for defense in World War I.

World War I revolutionized combat. For centuries, European armies had relied on disciplined infantry ranks and speedy charges from calvary, but advances in weapons technology made those techniques almost useless by 1914. French military commanders had to completely rethink their strategy during World War I.

Outdated Tactics

At the beginning of World War I, French military tactics lagged behind modern weaponry. At first, the French relied on massive assaults and large defensive fortifications that had proved successful in previous conflicts, according to historian Roger Daene, writing for Military History Online. These tactics failed in the face of barbed wire, machine guns and modern artillery. Tens of thousands of French troops died in hapless charges into the teeth of German defensive lines. By the end of 1914, the first year of the war, 850,000 French troops were dead or wounded.

Trench Warfare

Eventually, the many belligerents in World War I adapted their strategy and tactics to new military technologies. Both French and German forces dug trenches along the western front to shield soldiers from enemy fire. The French dug trenches in a zigzag pattern to provide extra cover against enemy machine gun fire, but life in the trenches was dire. Rats, the smell of rotting corpses, and the constant threat of grenades and artillery shells haunted soldiers constantly. The trenches provided some cover from enemy fire, but also exposed soldiers to disease.

Assault and Infiltration Squads

In the 19th century, armies had defeated their enemies with massive charges of infantry divisions. The realities of machine guns and other strong defensive weapons rendered those tactics impossible. French forces adapted by relying on infiltration tactics, a technique featuring small squads sneaking up on the enemy from the side or the rear. The new technique attempted to isolate pockets of enemy forces, while avoiding the insurmountable defensive weapons on the front line. The tactic was often successful, and German, British and American forces also used it.

Chemical Warfare

One of the most horrific aspects of World War I was the widespread use of chemical weapons, especially poisonous gas. The Germans were the first to use chemical weapons, lobbing gas shells into enemy trenches to force opposing soldiers out of their cover. By mid 1915, the French and British began using chlorine and mustard gas on a regular basis. The French supplied gas masks to their forces, though the masks were of poor quality and often failed. By the end of the war, gas attacks were so common that the French made gas masks for horses and dogs. An estimated 52,000 civilians died in gas attacks during the conflict.