A mustang is United States Military (especially Navy and Marine Corps) slang for a commissioned officer who began his or her career as an enlisted person. Mustangs are usually older and more experienced than their peers-in-grade who earned their commissions from one of the several service academies (ie. the United States Naval Academy), Officer Candidate School or the Reserve Officer Training Corps. The United States Department of Defense, abbreviated DoD or DOD and sometimes called the Defense Department, is a civilian Cabinet organization of the United States government. ... Seal The United States Department of the Navy was established by an Act of Congress on April 30, 1798, to provide administrative and technical support, and civilian leadership to the United States Navy. ... Slang is the non-standard or non-dialectal use of words in a language of a particular social group, and sometimes the creation of new words or importation of words from another language. ... In military organizations, a commissioned officer is a member of the service who derives authority directly from a sovereign power, and as such holds a commission from that power. ... In military service, an enlisted rank is generally any rating below that of a commissioned officer. ... The United States Naval Academy (USNA) is an institution for the undergraduate education of officers of the United States Navy and Marine Corps and is located in Annapolis, Maryland. ... In the United States armed forces, Officer Candidate School (OCS) or the equivalent is a training program for non-commissioned officers, soldiers, Sailors, Marines, Airmen and recent college graduates to earn commissions as officers. ... The Reserve Officer Training Corps (ROTC) is a training program of the United States armed forces present on college campuses to recruit and educate commissioned officers. ...

Navy mustangs can be Limited Duty Officers, Staff Officers or Unrestricted Line Officers depending on their particular situation. Warrant Officers are usually not referred to as mustangs. A Limited Duty Officer (LDO) is an officer in the U.S. Navy or U.S. Marine Corps who was selected for commissioning based on his skill and expertise, and are not required to have a Bachelors Degree. ... Staff officers in the U. S. Navy provide specialized support to Line Officers and to all other persons in the organization. ... Unrestricted Line Officers are Officers of the Line in the U.S. Navy who are qualifed to command ships of the line (ships of war). ... A Warrant Officer (WO) is a member of a military organization holding one of a specific group of ranks. ...

All Marine Corps Officers (mustang and non-mustang) are Line Officers, except for Warrant Officers and Limited Duty Officers. A line officer (or otherwise termed officer of the line) is a military officer who is trained to command a warship, ground combat unit or combat aviation unit. ...