Is anyone aware of the evolution of war? I'm specifically looking for the number of combatants as a function of time. I imagine "war" started as relatively small clans/families fighting, evolving over time into cities and states clashing. I'm interested in what would be considered a "large" battle at different stages of history. For instance, around 2000BC, would a conflict involving 10k be considered huge? How about 1000AD?
The number of troops involved in battle has ebbed and flowed through history. Of course, one runs into the problem of inaccuracies in documentary evidence, whether from lack of real knowledge or propoganda.
The Egyptians appear to have fielded armies of thousands of men at times. If you accept Rameses the Greats claims about his campaigns then his army number somewhere between 5000 and 10000 men. But it is generally accepted that his claims are exaggerated.
Later, during the Classical Greek period we have very accurate figures for Greek armies from Herodotus and Thucidides. However, if Herodotus is to be believed regarding then Persians then they were fielding an army of about half a million. Most scholars agree that the actual force was more like 10 to 20 percent of this number. Herodotus was amplifying the threat to Greece posed by Persia. Later in the period, the time of the Pelopponesian War, armies were smaller. Gylippus invaded Sicily and besieged Syracuse with a force of about 5000, mostly raised in the Sicilian hinterland.
Alexander's armies of the Hellenistic period were large, about 10000 to 20000, but for the most part they were quite static. The infantry held the enemy while the cavalry swept the flanks and delivered a decisive blow to the rear. The Persian armies he faced were similarly large, larger, in fact, than his own force. Alexander's successors maintained the general pattern of his army but varied numbers depending on where they were and the level of outside threat.
Republican Rome had a base legion of 4800 men and generally put two into the field at a time, for a force of about 10000 men. The size of the legion increased in the late Republic to 5500 and later during the Imperial period to 6000. An Imperial legion, however, was always accompanied by a legion of auxilliaries. So when one reads of four legions taking the field, the writer is only referring to the regular troops. Thus four legions is not 23000 or so but more like 45000 to 50000. Big numbers!
Toward the end of the Empire this practise died out and a legion was not supported by auxilliaries in the same way. Roman armies set the tone for the Dark Ages and consequently armies were considered large at 5000 troops.
Around AD1000, the time of the Norman invasion of England. The same military pattern was still used. So the armies that met at Stamford Bridge and Hastings in 1066 were 5000 or less men.
I hope this potted view of history helps somewhat.