From Wikipedia

Warriors of the French Foreign Legion

The French Foreign Legion (French: Légion étrangère) is a unique unit in the French Army, established in 1831. The legion was specifically created for foreign nationals wishing to serve in the French Armed Forces, but commanded by French officers. However, it is also open to French citizens, who amount to 24% of recruits. After the July Revolution of 1830, foreigners were forbidden to enlist in the French Army, and so the Legion was created to allow France a way around this restriction. The Legion was also seen as a convenient way to dispose of numerous recently-displaced foreign nationals (many of whom were thought to hold revolutionary political beliefs) by sending them to Algeria to help in the conquest.

The Legion was primarily used to protect and expand the French colonial empire during the 19th century, but it also fought in almost all French wars including the Franco-Prussian War and both World Wars. The Foreign Legion has remained an important part of the French Army, surviving three Republics, one empire, two World Wars, the rise and fall of mass conscript armies, the dismantling of the French colonial empire and the French loss of the legion's homeland, Algeria.

The Legion is today known as an elite military unit whose training focuses not only on traditional military skills but also on its strong esprit de corps. As its men come from different countries with different cultures, this is a widely accepted solution to strengthen them enough to work as a team. Consequently, training is often described as not only physically challenging, but also extremely psychologically stressful.