Shield Formation is a military tactic used by infantry units to create a protective barrier against enemy attacks. Soldiers align themselves closely, holding their shields in a way that covers themselves and their comrades. This formation is effective in defending against projectiles and can also be used to advance toward the enemy while maintaining protection. Historically, Roman legions famously employed shield formations, such as the testudo, where soldiers would interlock their shields to form a nearly impenetrable wall. This tactic allowed them to move safely in battle, providing both defense and a means to close in on opponents.