forces of the United States introduced service numbers in 1918, and discontinued their use in 1974. In 2011, the Department of Defense began implementing a new service number system in order to reduce identity theft. The first U.S. military member to hold a service number was Arthur Crean. The following formats were used to denote U.S. military service numbers: 12-345-678: United States Army and U.S. Air Force enlisted service numbers 123-45-67: United States Navy enlisted service numbers 1234-567: United States Coast Guard enlisted service numbers 123456: United States Marine Corps enlisted service numbers 12345: Service number format for most U.S. military officers Social Security Numbers are today used as the primary means to identify members of the U.S. military. The common format for social security numbers is 123-45-6789. Effective June 2011, the US military has introduced a plan to eliminate the use of Social Security Numbers on military and dependent ID cards, and replace them with a service number, in an effort to prevent identity theft against members of the armed services. All members have now been issued a DoD ID number for this purpose. References Identifiers Military life