The Paris Gun, one of World War I’s most formidable and terrifying weapons, was a giant artillery piece that reached unimaginable distances and heights, striking fear into the heart of Parisians.

The advance into Paris began early in the morning -- just five weeks to the day after the German invasion of the Low Countries and the beginning of "real" warfare against the British and French.

Germany captures Paris, and France surrenders to the Nazis ... Germany is able to maintain weapons and aircraft production levels. The Allied invasion of France commences; troops based in England ...