She set out to save a species...us. An intimate portrait of the woman whose groundbreaking books revolutionized our relationship to the natural world.

Part 1 of 3. President Woodrow Wilson vowed to keep the U.S. out of World War I after hostilities erupted in Europe in August 1914. It was a promise he kept until 1917, when the Germans resumed "unrestricted submarine warfare"— a policy it had started and then stopped in 1915 — and began sinking U.S. ships. An intercepted telegram also showed Germany trying to convince Japan and Mexico to declare war on America.

Part 2 of 3. America's entry into World War I is recalled, including the breathtaking speed of mobilization and the profound transformations required for America to play a central role in the conflict.

Part 3 of 3. In the fall of 1918: a major American offensive that could bring a swift end to the war, a lost U.S. battalion surrounded by German forces, a deadly flu epidemic on the homefront.