Just for fun, let's look at some of the armed forces figures for WWII. These are approximate, include only the major nations (Chinese figures are not reliable) and of course not every member of a nation's armed forces carried a rifle or other small arm. Still...
U.S. 12,209,000
USSR 33,000,000
UK 3,000,000
Germany 18,200,000
Japan 5,500,000
Total 71,700,000
That folks, is a whole lot of (mostly) men and a lot of small arms. Plus police, para-military (like the Gestapo) are not included, although they were armed.
We know that millions of those arms were destroyed in combat, millions more scrapped by their captors, millions more dispersed around the world to small nations or political "fighters" of various kinds, mostly not under any kind of government control.
Jim