Which Allied invasion saw the first large-scale use of the DUKW?

The first large-scale Allied invasion use of the DUKW was during the invasion of Sicily, Operation Husky.

The DUKW was a six-wheeled amphibious truck based on the GMC CCKW 2½-ton truck. It could drive from a ship into the water, paddle to shore using a propeller, and then continue inland on its wheels. That eliminated much of the repeated unloading and reloading normally required between ship, landing craft, and beach.

During the Sicilian campaign, which began on 10 July 1943, DUKWs moved troops, fuel, ammunition, and other supplies across beaches before suitable ports were fully available. Their ability to keep cargo moving over the shoreline helped address one of the central logistical problems of amphibious warfare.

The vehicle was also used earlier in the Pacific, including at Guadalcanal, so “Sicily” means the first use by an invasion force in the European theater—not the first appearance of a DUKW anywhere. Later, large numbers served at Normandy and in other Allied operations.