And that unit discipline became more important depending on the fighting philosophy used by a given country. In the hundred years war, it wasn't uncommon for the British to dismount and form a line to support the yeomanry/archers. At Agincourt Henry actually sent his horse to the rear (such as it was). If the British broke lines, it gave the French with their tendancy to emphasize cavalier tactics the ability to win. Which didn't happen all that much, so the discipline of the British line was one of the elements to their success. If they had routinely broken up into random melee the latter part of the hundred years war would have been much shorter.
And pitch battles like Agincourt, weren't the most common form of warfare in the hundred years war. Sieges of towns were important,and to arrange lines to cut off a citadel, and to ensure relief forces were blocked...entailed close discipline amongst units. And when cannon were involved, unit discipline was often what kept British units intact agaisnt the new terror weapon. At the battle of the Herrings, despite the French cannons, and the charge of vengeful Scots, the British didn't break lines.
And the later pike squares were so effective (and survived) because of group discipline...often a bunch of townsmen could beat the cavalier class.
So as noted, the single combat/movie paradigm wasn't that common. Nor is it a condition limited to the west. And when the Japanese first fought the Mongels (in the early Mongel raids into Japan) and tried to use the naming and calling out tradition of the samurai...the Mongels usual response was a hail of arrows and the Parthian shot. ..and resultant dead samurais.
