Between the end of WWII in 1945 and the beginning of the Korean War in 1950, Willys-Overlandhad been producing the new "Civilian" Jeeps called CJ-2A's followed by the CJ-3A's.
Willys began reviving it's Military Jeep production for the Korean War by upgrading and renaming its CJ-3A to be called the M38. The M38 was essentially the CJ-3A but had a one-piece windshield, conventional wiper, larger headlights and a more durable rear axle, among other improvements.
Although Willys built over 60,000 M38's they were replaced by a totally new, improved design in 1952 called the M38A1. The M38A1 would shortly become the prototype of the soon to arrive now famous CJ5 in 1954.