How Many People Do You Have to Have to Be in a Battle?

The average size of battle seems smaller now in the european theater. The battles that would be considered too tiny to even count as battles in other places and times count i mean you could have 900 guys against 900 guys in anglo-sax and england but a thousand years before this period that's a reconnaissance clash between the Romans and the Carthaginians or one of the puneque wars. How many people do you have to have to have an in in a military encounter to call it a battle is there a minimum number? That was a great question asked in hanstell brooks histories of more than a hundred years ago because they still touch us today.