Medieval world

The greatest battle of the Middle Ages was the Battle of Grunwald. The clash between the Kingdom of Poland and the Teutonic Order took place on the 15th of July 1410. 

An excerpt from the article 25 facts about Medieval world

It was a decisive battle between two huge armies, each numbering from a dozen to tens of thousands.

It is estimated that 50,000 people fought on the fields of Grunwald. This was a huge number of troops for the time, as most medieval battles involved at most a few thousand soldiers.