The French Foreign Legion is the only military branch in the world open to people of any nationality!
The FFL was established in 1831 and is lead exclusively by French officers, but it open to all nationalities to serve in.
Today, the legion is known as an elite military unit. The training is said to be both physically and psychologically straining due to the culture shock the soldiers face.
They conquered Algeria to create colonies from 1830-1847. They assisted Spain, fought the Crimean War and numerous others since then.