military unit: Quick Facts

Written and fact-checked by

The Information Architects of Encyclopaedia Britannica

Photos

Diagram of a Macedonian battle formation showing a central block of 4,096 hoplites flanked by 1,024 psiloi in front, 2,048 peltasts behind, and 512 cavalry on each side, illustrating the simple phalanx perfected by Philip II and Alexander the Great.

Diagram comparing early Roman legion formations around 220 BC, with four types of maniples arranged in rows, to the Marian legion around 110 BC, which is organized into 10 larger cohorts.

A chart displaying the hierarchy of United States Army operational units, from squad to field army, with each unit's typical size, structure, and the rank insignia of the commanding officer listed alongside.

A comparison chart displays the officer rank insignias for the United States Army, Marines, Air Force, Space Force, Navy, and Coast Guard, with each rank represented by its corresponding badge, bar, leaf, eagle, or star symbols.

Juno Beach, Normandy Invasion

Two British Navy aircraft carriers, HMS Albion in the foreground and HMS Centaur behind, sail at sea with aircraft lined up on their decks.

Republic F-84 Thunderjets

See All Images →

Topics

legion phalanx wing air group air division squadron army corps field army flotilla naval fleet commando Joint Chiefs of Staff Military law war college navy conscription knight paramilitary all-volunteer force military, naval, and air academies