Gen. Dwight D. Eisenhower had a problem. In June 1944, Allied forces had landed on Normandy Beach in France and were moving east toward Nazi Germany at a clip of sometimes 75 miles (121 kilometers) per day.

With most of the French rail system in ruins, the Allies had to find a way to transport supplies to the advancing soldiers.

“Our spearheads … were moving swiftly,” Eisenhower later recalled. “The supply service had to catch these with loaded trucks. Every mile doubled the difficulty because the supply truck had always to make a two-way run to the beaches and back, in order to deliver another load to the marching troops.”

The solution to this logistics problem was the creation of the Red Ball Express, a massive fleet of nearly 6,000 2½-ton General Motors cargo trucks. The term Red Ball came from a railway tradition whereby railmen marked priority cars with a red dot.