Strategically, the majority of the first World War was fought as a stalemate. Most of the combat occurred in trenches on the western front, with very little chance for guerilla warfare and extended periods of combat in close proximity. Both sides dug miles of trenches so that they would not be exposed to enemy fire. Whenever one of the sides tried to move across no-man’s land in between the lines of trenches, they were typically gunned down by heavy artillery, so the front never moved more than a mile or two in either direction.
Even though neither side had a clear advantage, that does not mean that the war was not a display of a myriad of new weapons and techniques. Rifles and machine guns were introduced for the first time in battles during the war, and they proved to be much faster and more effective than the rifle-muskets that had been previously used. Both sides turned to the use of tanks and airplanes to help break the stalemate they faced. Tanks, although somewhat slow and reliable, helped in battles such as that at Amiens in 1918 when the British army took the German line. Airplanes were used mainly to scout, as they were not yet technologically capable of strong aerial bombardments.
World War 1 was the first time chemical weapons were used in battle, and these new innovations proved to be instrumental in making progress in combat. Germany first used cylinders of chlorine gas against the French in April of 1915 at Ypres. The gas, when inhaled in large amounts, was able to destroy the respiratory systems of the soldiers, although because it stimulated coughing, often the soldiers did not take in a deadly amount. Both sides began using a mixture of chlorine and phosgene called “white star,” which proved to be much more effective. It immediately forced the soldiers to stop fighting and killed them within just 48 hours.
In September of 1917, the German army introduced a new chemical weapon: mustard gas. It was odorless and fatal in 20% of the people who came into contact with it, in comparison to just 1% with the chlorine and phosgene gas. Mustard gas caused internal and external bleeding, blisters on the skin, sore eyes, and the deterioration of the bronchial tubes. The introduction of these chemicals as weapons in war caused thousands of casualties and forced troops on both sides to alter their tactics to prevent against crippling attacks by these gases.
Steven Miller, Military Strategy and the Origins of the First World War, 1991
Paul Boyer, The Oxford Companion to United States History, 2001