depends on who you are and where you are at i guess. but my guess would be a no to the answer... unless your Roman or Greek, then maybe there cause you actually move as a group not the individual.
for instance: 15thc England. most soldiers are Yoeman following a minor Lord/Baron. they stick close to him due to they are probably part of his retinue. they don't intermingle that much. there are no standing armies at this time, it's illegal. we even have written documentation of a solider killing another on the same side just in a different household/retinue due to the feuding of their Lords.
Even the crusades had nobility and soldiers from different populations, and areas. Do you think they were going to join up and march with another foreign group just because they were on the same side? I'm not so sure about that one. (ie a Frenchman would want to march with an Englishman? not hehehe)