Why do I have to join the French Foreign Legion under an assumed name?

A defining characteristic of the legion is its rule of anonymat (French for “anonymity”), which says that all Legionnaires must give up their civil identity upon enlisting. In many ways­, Legionnaires are shedding their former national identities for a new French identity. On the next page, we’ll look briefly at this history to gain some more insight into how and why declared identity became such a defining characteristic of the French Foreign Legion.

Source: science.howstuffworks.com