Janissaries

In Janissaries, the leader is a United States Army officer from the Cold War period, Captain Rick Galloway, who along with his platoon-sized unit of soldiers primarily from the U.S. are abducted from a CIA-run operation against Cubans in the fictional tropical African country of Sainte-Marie by a flying saucer. The beings abducting them present themselves as rescuers from a hopeless situation where Galloway's unit is about to be overrun by Cubans in a night assault, the aftermath of which is expected to be the deaths of all. Afterwards, the human soldiers have the option of serving the aliens in a special situation involving a more primitive planet on which there are humans living in medieval conditions. The soldiers are expected to be able to use their superior weapons and tactics to conquer part of the planet.