The basic building block of all Army organizations is the individual soldier.  A small group of soldiers organized to maneuver and fire is called a squad.  As elements of the Army's organizational structure become larger units, they contain more and more subordinate elements from combat arms, combat support and combat-service support units.  A company is typically the smallest Army element to be given a designation and affiliation with higher headquarters at battalion and brigade level.  This designation causes an "element" to become a "unit".

Soldier  The American Soldier is the basic building block of all Army organizations.

Squad  Nine to 10 soldiers.  Typically commanded by a sergeant or staff sergeant, a squad or section is the smallest element in Army structure.

Company  62 to 190 soldiers.  Three to five platoons form a company, which is commanded by a captain with a first sergeant as the commander's principal NCO assistant.  A artillery unit of equivalent size is called a battery, and a comparable armored or air cavalry unit is called a troop.

Battalion  300 to 1,000 soldiers.  Four to six companies make up a battalion, which is normally commanded by a lieutenant colonel with a command sergeant major as principal NCO assistant.  A battalion is capable of independent operations of limited duration and scope.  An armored or air cavalry unit of equivalent size is called a squadron.

Division  10,000 to 15,000 soldiers.  Usually consisting of three brigade-sized elements and commanded by a major general, divisions are numbered and assigned missions based on their structures.  The division performs major tactical operations for the corps and can conduct sustained battles and engagements.

Corps  20,000 to 45,000 soldiers.  Two to five divisions constitute a corps, which is typically commanded by a lieutenant general.  As the deployable level of command required to synchronize and sustain combat operations, the corps provides the framework for multinational operations.

Army  50,000+ soldiers.  Typically commanded by a lieutenant general or higher, an army combines two or more corps.  A theater army is the ranking Army component in a unified command, and it has operational and support responsibilities that are assigned by the theater commander in chief.  The commander in chief and theater army commander may order formation of a field army to direct operations of assigned corps and divisions.  An army group plans and directs campaigns in a theater, and is composed of two or more field armies under a designated commander.  The army since World War II has not employed army groups.

** Source: Soldiers Magazine 2004 Almanac.