World War I was the first "world war," in the sense that the conflagration wasn't just between two countries, but between large blocks of countries, intertwined in complex alliances. The model of the entire world being caught up in conflicts would continue in World War II and in the Cold War. World War I was a testing ground for weapons and ideas that would impact the rest of the 20th century. Sometimes the innovations of World War I were technological in nature - U-boats, poison gas, machine guns, heavy artillery, tanks and battleships were all used either for the first time in World War I, or first used on a wide-scale in World War I. Sometimes, the impacts were from strategy and tactics - trench warfare, convoys and etc. And sometimes the innovation was a political idea. Communism as an actual political and economic system, rather than just a philosophy, debuted in World War I, and would have a worldwide influence until its fall in 1991. The book contains over 50 illustrations and maps.