Tactical formation

A tactical formation (or order) is the arrangement or deployment of moving military forces such as infantry, cavalry, AFVs, military aircraft, or naval vessels. Formations were found in tribal societies such as the "pua rere" of the Māori, and ancient or medieval formations which include shield walls ("skjaldborg" in Old Norse), phalanxes (lines of battle in close order), Testudo formation and skirmishers. 
Tactical formations include:
A vanguard