How to be a soldier in a foreign army?

The first choice, mercenaries, don't think that mercenaries only exist in novels. This does exist. The second choice is to turn yourself into a foreigner. I mean documents and the like, that is, so-called immigration and the like. How to go to the United States to serve as a soldier: Originally, the American army did not recruit foreigners, but the shortage of soldiers has been increasing in recent years, coupled with Iraq and Afghanistan. ...