When they started issuing everyone a machine gun.This brings to mind another question:
When I was a kid, every other kid I knew (well, almost) their dads had pistols, Carbines, Garands, 03s, and not to mention German and Japanese weapons they brought home from WWII.
When did they change all that bring backs?
When returning from WWII and Korea, duffle bags weren't inspected like they are today or during Vietnam. In fact, I went back and forth to Germany, in uniform on a civilian aircraft, with a folding stock M1 carbine and a Beretta pistol in my duffel bag. No one on either end cared. I just showed my military ID and travel orders and they waved me right through Customs.
During WWII and Korea, lots of pistols and rifles were listed as lost or battle damaged, when they actually ended up in duffel bags. It was up to local unit commanders to decide who got away with what.