World War I was the first truly modern war. It was the first war in which mechanized warfare was carried out on a large scale. Mechanized warfare simply refers to the use of advanced machinery in war. On land, World War I was characterized by trench warfare, in which men would dig complex systems of trenches in order to provide a defensive position. Conditions in these trenches were appalling. The tank was invented during World War I by the British. The first tank, the British Mark 1, saw action during the Battle of the Somme in 1916. Poison gas was also first used on a large scale during World War I, prompting soldiers to wear gas masks. Mustard gas and chlorine gas were two of the most popular chemical agents used in gas attacks.

Germany developed a formidable fleet of submarines, or U-boats, and used them to target Allied merchant vessels in the Atlantic. World War I was also the first war in which the airplane saw widespread use. One of the most famous aces of the war was the German pilot Manfred von Richthofen, commonly known as the Red Baron. If there is one thing you should remember about the Great War, it is that it was a war of firsts: the first use of mechanized warfare and chemical warfare, the first use of the tank, and the first widespread militarized use of the submarine and airplane.