The "armed conflict" was r=the Spanish Civil War. The War which was between Communist and Fascist forces (with a few smaller factions). Many Americans went over to fight for various reasons, mostly to prevent Fascism, however there were also those fighting against communism, with the smaller, and also just for adventure. One of the most well known Americans that went over to fight was Ernst Hemingway.
Many consider it a prelude to World War 2 given that the end led to another Fascist power rising, which was financially ans militarily backed by fellow Fascist nations of Germany and Italy, and the Communists by the Soviet with many other nations having soldiers volunteer.
In the end it left many of those who participated with scars both physical and psychological, given that it was a very intense and vicious war (another reason it is considered a prelude yo WWII) and Spain with a Fascist dictatorship until the leader died in the early 70s.
It was also used as the backdrop for the movie Pan's Labyrinth.
Lol, sorry but I'm guessing you had meant to reply to Blargh?