Major events are often rooted deeply in the past—the “long fuse” that leads to explosions.

Just a few months after Adolf Hitler came to power in Nazi Germany and a full six years before World War II, German university students carried out an “Action Against the Un-German Spirit” targeting authors ranging from Helen Keller and Ernest Hemingway to Albert Einstein and Sigmund Freud. Their orchestrated book burnings across Germany would come to underscore German-Jewish writer Heinrich Heine’s 19th century warning, “where one burns books, one soon burns people.

Despite their early agreement on a strategy focused on defeating “Germany First,” the US and British Allies engaged in a lengthy and divisive debate over how exactly to conduct this strategy before they finally settled on a plan for Operation Overlord, the D-Day invasion of Normandy.

Often overshadowed by the Battle of Midway, the hard-fought carrier naval battle in May 1942 in the waters of the Coral Sea north of Australia marked the end of the phase of Japanese triumphs in the Pacific War and proved to be of strategic significance.

From our 21st-century point of view, it is hard to imagine World War II without the United States as a major participant. Before the Japanese attack on Pearl Harbor in 1941, however, Americans were seriously divided over what the role of the United States in the war should be, or if it should even have a role at all. Even as the war consumed large portions of Europe and Asia in the late 1930s and early 1940s, there was no clear consensus on how the United States should respond.