Book excerpt: When America entered World War I, it seemed as though the world had turned upside down. Many new technologies were developed on both sides of this conflict, challenging the men and women who fought in it in ways they never could have imagined. Among these developments were the military tank, the tracer bullet, and most deadly of all, poison gas. This book examines the times and events of the war, the key technologies that influenced and affected it, and the lasting impact these had on global society.