Understanding Military Culture

Service Branches

Service Members

U.S. Army

Founded in 1775, the Army is the oldest branch of the military.

Approximately 549,015 full-time soldiers in today’s Army defend and serve our nation by land, sea and air.

In addition to domestic bases, the Army has permanent stations in Asia, Europe and the Middle East, as well as troops on the ground wherever there is a conflict.

U.S. Navy

The Navy was founded under the authority of George Washington in 1775.

Currently comprised of 324,239 personnel, today’s Navy is equipped to handle operations both on and under the sea, in the air and on the ground. A sailor generally serves a term of four years aboard one of the Navy’s 283 deployable ships.

U.S. Marine Corps

The Marine Corps was founded in 1775.

Today, 203,075 Marines are stationed around the world at all times, ready to deploy quickly whenever and wherever needed. The Marine Corps plays a major role as the first force on the ground in most conflicts.

U.S. Air Force

The Air Force began as a subdivision of the Army and was declared an official combatant arm in 1920. U.S. Army Air Corps. It wasn’t until 1947, following WWII that the Air Force was recognized as its own branch.

The Air Force is a technologically advanced force of 328,847 troops focused on air, space and cyberspace superiority.

U.S. Coast Guard

In 1915, a congressional act combined the Life-Saving Service and Revenue Cutter Service to form the Coast Guard.

In 1967, executive order transferred the Coast Guard to the newly formed Department of Transportation.

The Coast Guard now operates under the Department of Homeland Security during peacetime and under the Navy during wartime; or by special presidential order. The 42,426 active duty members of the Coast Guard perform search and rescue, law enforcement and environmental cleanup operations.

U.S. Reserve Military Personnel

Reserve components generally train one weekend per month and two weeks per year.

Army Reserve/National Guard: 205,297
Navy Reserve: 119,307
Air Force Reserve/Air National Guard: 67,987
Marines: 46,688
Coast Guard: 7,693

Military Status

Active Duty

Full-time active service in the U.S. Military (Army, Navy, Air Force, Marines, Coast Guard). This includes members of the Reserve components serving on active duty but does not necessarily include all National Guardsmen serving full-time.

Drilling Reserve

Part time military service usually consists of one weekend a month and two weeks a year. When reserve forces are mobilized for full-time active duty service they serve on active duty until demobilized, at which point they revert back to drilling status.

National Guard

A reserve component of the U.S. Armed Forces, the National Guard is a state militia that answers first to the governor, but can be put into federal service by order of the president. Call up by the state is not considered “active duty”.

Activated Guard and Reserve

National Guard and Reserve members, who have been mobilized into active duty, usually do so for a period of six months or one year.

Number of Veterans by Era

Service Member

Approximately 25 million veterans live in the United States.

The states with the highest concentrations of veterans are California, Florida, Texas, New York, and Pennsylvania.

  • WWII (1941–1945): 2.6 million (1,000 die per day).
  • Korean War (1950–1953): 2.8 million.
  • Vietnam (1961–1975): 7.8 million.
  • Gulf War I (August 1990-August 2001): 2.9 million (Desert Shield, Desert Storm, Desert Calm).
  • Gulf War II (September 2001–present): 2.2 million (Operation Enduring Freedom, Operation Iraqi Freedom, Operation New Dawn [OEF/OIF/OND]).
  • Non-combat era: 6.6 million

Military Lingo

Members of the military are referred to differently depending upon their specific Service.

  • Soldiers – Members of the Army
  • Sailors – Members of the Navy
  • Airmen – Members of the Air Force
  • Coast Guardsmen – Members of the Coast Guard
  • Marines – Members of the Marine Corps
  • Guardsmen – Members of the National Guard
  • Reservists – Members of the Reserve

Official Acronyms

  • AWOL – Absent With Out Leave: not at one’s place of duty and not authorized to be absent
  • CDR – Commander
  • CO – Commanding Officer
  • CONUS – Continental United States
  • COB – Close Of Business: the end of the day or duty shift
  • CoS – Chief of Staff
  • DD or DoD – Department of Defense
  • IAW – In accordance with
  • ICO – In case of, in care of
  • IED – Improvised Explosive Device
  • IRT – In reference to
  • GWOT – Global War On Terror
  • NCO – Non-Commissioned Officer: an enlisted person with command responsibility over soldiers of lesser rank
  • NCOIC – Non-Commissioned Officer In Charge
  • OEF – Operation Enduring Freedom: official name used for the War in Afghanistan
  • OIF – Operation Iraqi Freedom: official name used for the War in Iraq
  • OND – Operation New Dawn: new name for the War in Iraq starting in September 2010 to reflect reduced role of US troops
  • MOS – Military Occupational Specialty: job or career specialty (e.g., infantryman, intelligence analyst, operating room specialist, military police, etc.)
  • OCONUS – Outside the Continental United States
  • POC – Point Of Contact: the person to liaise with on a given matter
  • ROTC – Reserve Officer Training Corps (often pronounced “ROT-SEE”)
  • R/S – Respectfully Submitted: used as an end greeting in written communication or email
  • SOP – Standard Operating Procedure: the routine manner of handling a set situation
  • TDY – Temporary Duty Yonder
  • V/R – Very Respectfully: used as an end greeting in written communication or email


  • Battle assembly – new term used for Army Reserve weekend drills, unit training assemblies, or multiple unit training assemblies
  • Boots on the ground – to physically be in a location (some may use this to say that they want “boots on the ground” for a particular project, which means they want everyone physically in the office, rather than having people call in.)
  • Drill – preparation of military personnel for performance of their duties through the practice and rehearsal of prescribed movements; members of the National Guard and Reserve are required to attend one weekend drill a month (sometimes starting Friday night until Monday morning)
  • Extended drill – extended time for drill in preparation for a deployment
  • Liberty – authorized free time ashore or off station, not counted as leave, also known as a “pass”
  • Ma’am – proper method of addressing female officers in particular and women in general
  • Sir – proper method of addressing male officers in particular and men in general
  • Tour of duty – time period during which a particular job or assignment is done (e.g., my tour of duty is 8am-5pm)