Used to pay U.S. military personnel in foreign countries, Military Payment Certificates (MPC) were issued from the end of World War II until a few months after the end of the Vietnam War. Fifteen series of MPC notes were created, though only thirteen series were issued to servicemen. MPC were created to prevent U.S. notes from being used as the primary currency in the host country of an ongoing military conflict. Most were redeemed for an equivalent amount of U.S. currency, though some were kept as souvenirs.