US servicemen in WWI

The term "doughboys" comes from US cavalrymen's derogatory term for food soldiers.  They marched behind the troops on horses and as a result got covered in dust that resembled "adobe" which was a building material of the time.  Thus the foot solders became "doughboys".  A second theory has it that the term comes from the large button worn on uniforms that looked like lumps of fried dough.

Shotgun (weapon) was called a "trench broom" and the Germans complained it was a "violation of rules of war"

French railroads kept records of the number of US troops transported by rail and sent the AEF a bill "for their fares".  The French had a good relationship with US soldier because they drank a lot which increased the price of champaign and cognac.

Mustard gas would eat fresh (like lye) and destroy testicles of a solder jumping into a pit that had gas in it.  May be what happened to the Ernest Hemingway character in "The Sun Also Rises", Jack Barnes had become impotent in this manner.

Mustard gas (and chemical agents) wounds caused "disfiguring".  This resulted in "many American cities in 1919 and into the 1920's passing laws about being seen in public..."  Did not want to scare women and children.  Those disfigured were required to "be hooded or masked".  It was a crime for "being ugly on the public way" (Chicago term).  The American Legion founded post WWI.  Some vets excluded if they were suspected of "having ties to radical labor or bolshevist leanings...".  The vets who served in Siberia (Russia) were "particularly affected and considered "tainted by the experience".

(Source: US Servicemen in WWI)