The armed forces of many nations have, at one time or another, used foreign volunteers who are motivated by political, ideological or other considerations to join a foreign army. These may be formed into units of a given nationality or may be formed into mixed nationality foreign units. Sometimes foreign volunteers were or are incorporated into ordinary units. The practice has a long history, dating back at least as far as the Roman Empire, which recruited non-citizens into Auxiliary units on the promise of them receiving Roman citizenship for themselves and their descendants at the end of their service.

Mixed nationality units

Historic

Current

Also including nationals

Only including foreigners

Units by nationality

American

During both world wars, American volunteers served on the allied side before the US joined the war. During World War I, there were even a few Americans who volunteered to fly for the Imperial German Flying Corps.

Albanian

Bangladeshi

Belgian

British

Bulgarian

Bosnian

Canadian

Chinese

Croatian

Czech

Estonian

Filipino

Finnish

French

German

Greek

Indian

Irish

See also Irish military diaspora.

Israeli

Italian

Japanese

Korean

Moroccan

Nepalese

Polish

Portuguese

Rhodesian

Russian

Serbian

Scottish

South African

Spanish

Swedish

Swiss

Taiwanese

Ukrainian

Yugoslav