Here were the best picked men
detached in squads to stand the Trojan charge
and shining Hector: a wall of them bulked together
spear-by-spear, shield-by-shield, the rims overlapping,
buckler-to-buckler, helm-to-helm, man-to-man massed tight
and the horsehair crests on glittering helmet horns brushed
as they tossed their heads, the battalions bulked so dense
shoulder-to-shoulder close, and the spears they shook
in daring hands packed into jagged lines of battle
single minded fighters facing straight ahead,
Achaeans primed for combat.

– Homer

The Iliad, Book 13, lines 152-162. The Achaeans are massed in a tight wall and primed for combat, after Poseidon rallies them to fight the Trojan charge led by Hector.