How did soldiers from a unit manage to stick together during battles, if they managed at all? I imagine that getting a few hundred men to stand in a rough square is easy enough, but get them to march, run, fight, protect themselves from arrows, adopt different formations (not to mention the ever-present danger of cavalry charges in the rear and flanks) and sticking together seems to get considerably harder.

So how did soldiers manage to maintain a rough formation under crisis? The HBO Series Rome shows Roman soldiers holding on to each other's shoulders (the guy in the back holds onto the guy in front of him, and the guy in front holds onto the guy in front of HIM, etc etc) This seems to be pretty logical for sword units but what about spearmen, or levies? Did they bunch together? Link arms? Maybe tie a flimsy rope around their waist, linking them to the rest of the unit? (although in retrospect that last one doesn't seem to be particularly plausible, since if the rope were too taut then if one soldier fell, they'd all fall)

Any thoughts?