Was the Thompson used in ww1?

Answer 1

No. General Thompson was inspired to design it as a "trench broom" by the conditions of WWI, but few were finished by the time the war ended. Thompson then had trouble selling the weapon to the US Military (but you could buy one for $400 at Sears & Roebuck). Eventually the Marine Corps started buying some, and it was adopted as the Model 1928. The Browning Automatic Rifle had a similar story. Its more associated with WWII, but the BAR is the Model 1918 and a few did reach France before the fighting ended. Most WWI American automatic riflemen were equipped with the French Chauchat, an execrable weapon that got a lot of them killed as it jammed continually. The detachable box magazines had the sides cut out, I suppose so the operator could visually determine how many rounds remained in the magazine, but in conditions on the Western Front this allowed the introduction of mud and dirt into the mechanism, which was temperamental enough when clean.