The late 19th and early 20th centuries saw the rise of modernism, a major shift in the cultural zeitgeist of a world that was changing very quickly with new technologies and industrial revolutions, driven by the promise of progress and the pursuit of universal reason and scientific truths. In art, this led to the avant-garde movements, such as surrealism, Dadaism, expressionism, and futurism. These were consciously developed movements with specific rules and conventions, often spelled out in manifestos. Art and theatre in these movements were experiments trying to find the best way for art to reveal truth. But the mass ethos of the cultural zeitgeist made another major shift with World War II. World War I had been brutal and unprecedented in scope and technology to kill efficiently, but World War II reached a level of advanced weaponry that could separate soldiers entirely from their targets, launching missiles and dropping bombs from airplanes, tanks, ships, and submarines. Killing from a distance was dehumanizing, and casualties reached as high as four to five times the already astronomical numbers of WWI. The Allied forces killed and injured hundreds of thousands of people from the air, including approximately 200,000 (mostly) innocent civilians in the devastating nuclear bomb attacks on Hiroshima and Nagasaki.