July 17, 2012: In the United States the non-citizens of prime military age (18-29) make up about 2.2 percent of the U.S. population, but 4 percent of military personnel. There are about 1.2 million non-citizens who are physically, mentally, and psychologically fit to serve in the military. These men and women are particularly attractive to the military because they tend to work harder, have fewer disciplinary problems, and often possess language skills and cultural knowledge that the military needs. But a major reason non-citizens are overrepresented in the military is that it's an ancient tradition for a newcomer to gain membership in the tribe/kingdom/country via performing some dangerous service to gain acceptance.
In the last decade the U.S. military has enlisted some 70,000 non-citizens, about five percent of all recruits. The foreign recruits are tossed out during their first three months of service at half the rate of their citizen counterparts. After three years of service 72 percent of citizens were still in uniform, compared to 84 percent of non-citizen troops. The foreign troops are more patriotic and work harder than their citizen counterparts. Non-citizen troops have another incentive, as they can apply for citizenship sooner because of their military service. Any foreign recruit forced out for medical reasons (because of combat or non-combat injuries) can still obtain citizenship more quickly. Most foreign troops obtain citizenship as soon as they can while in the military because many jobs require a security clearance and only citizens can get one of those.
In the last decade some senior American officers urged the recruitment of more foreigners. Not just non-citizens with green cards but foreigners who are not residents of the United States. This brought forth protests from those opposed to, well, whatever. Historically, the American military has usually had more foreigners in the ranks than it does now. During the American Civil War about twenty percent of the Union Army was foreign born troops. There were entire divisions of Irish, Germans, or Scandinavians. For the rest of the 20th century the all-volunteer military continued to have a higher (than today) percentage of foreigners. Recruiting foreigners enabled the army to get more enthusiastic and capable recruits Naturally they would have to speak acceptable English, just as resident foreigners in the United States or citizens from Puerto Rico must. The American military pay and benefits are competitive with U.S. civilian occupations but to most foreigners these pay levels are astronomical. The risk is low, as only about one in a thousand foreign born volunteers died in Iraq or Afghanistan. All that and you get to become a citizen of the United States after your four year enlistment is up. The only question was which line would be longer at American embassies, the one for visas or the one for military recruiting?
The United States is not alone in this acceptance of foreigners in the military. Take, for example, Britain. Two centuries ago Nepalese Gurkhas were first recruited into the British Indian army and then the British army. After India became independent in 1947, they too recruited Gurkhas for Indian infantry units. But service in the British army was considered a better deal. Britain has long recruited foreigners into its army and navy because there has always been a shortage of British citizens willing to serve.
Then there is the French Foreign Legion, which is supposed to be nothing but foreigners (except for the officers). But many French join, claiming to be from the French speaking parts of Belgium. No matter, if otherwise qualified the "Belgians" are signed up. In Italy, the Vatican (a small part of Rome that is an independent country controlled by the Roman Catholic Church) gets most of its security forces from Catholic areas of Switzerland. This is the Swiss Guard. While the French Foreign Legion dates from the 19th century, the Swiss have been serving as foreign mercenaries since the 15th century. But these contingents disappeared as better economic opportunities developed in Switzerland and mercenaries became less popular. Many other nations have successfully used foreigners in their armed forces. Not mercenaries but foreigners willing and able to serve next to the native born. It still works.