The end of the war draws near as the overwhelming number of American troops and their allies swing the conflict decisively away from Germany.

Tsar Nicholas II of Russia becomes the first emperor to fall in the conflict; the United States enters the war as mutinies break out on both sides.

After 16 months of fighting, neither side has gained any ground until a new machine is introduced, the tank.

Russia and Germany clash in the Battle of Tannenberg in August 1914; France defeats the German army in the Battle of the Marne; colonial troops join the global conflict.

The beginnings of the conflict known as "The War to End All Wars," including the assassination of Archduke Franz Ferdinand of Austria in 1914.

Remote sensing techniques tell the stories of WWII battles and campaigns, the details of which have been lost in the fog of war, misinterpreted or overtaken by the landscape.

This series helps change how people look at World War II thanks to hundreds of hours of video that have been declassified and fully restored in high definition. Soldiers on the front lines, secret operatives, resistance fighters, and private citizens shot the footage, some of which has never been seen, that gives viewers a firsthand look at what went on during times of battle. Episodes detail the battle over Stalingrad that was a key turning point in the war and show Japanese pilots on the morning of Dec., 7, 1941, preparing for the attack on Pearl Harbor.

Before the advent of air transportation, trains played a vital role during times of war. In addition to transporting soldiers and supplies to the front lines, the locomotives served as mobile hospitals and were sometimes used as massive weapons on wheels. "Combat Trains" explores some of the machines and railways that helped change history dating back to the Civil War. The show uses archival footage and accounts from veterans to highlight the stories of engineering prowess that helped the soldiers do their jobs.

Stories of some of the greatest and deadliest submarine patrols of World War II.

David Reynolds examines how the war haunted the generation who lived through it.