Aegis

Aegis: a shield, or protective armor; protective influence or power.

Aegis comes from the Greek word Αιγίς.  The Aegis was the shield of Zeus in Greek mythology.  Though made of goatskin, it was extremely strong.

These days, if you are under the aegis of someone, you are under their protection.

Example:  While serving overseas, they were under the aegis of the Peace Corps.