Studebaker US 6 6x4 tractor with trailer, Persian corridor, March 1943. A U.S. Army truck convoy carrying supplies for Russia is about to start as the leader checks with the first driver.
Although the GMC CCKW was the most numerous of the WW II 2 1/2-ton, 6x6 cargo trucks, almost 200,000 of the Studebaker-designed US-6 (G-630) were produced by Studebaker and another 22,000 by Reo from 1941-45. The cargo version was quite similar to the CCKW. The line haul version of the US6 was a 6x4 tractor for use with semi-trailers on improved roads.
The 2 1/2 ton 6x6 truck (the "deuce and a half" or just "deuce") was one of the logistical innovations that helped the Allies win World War II. The full story about the deuce trucks, including the World War II vintage Studebaker & Reo US6 Cargo Truck, is found on the linked page.