<human>:  Why did the Persians lose the war with Alexander the Great?
<bot>: The Persians lost because they were unable to defeat Alexander the Great in battle. Alexander had a huge army of about 50,000 soldiers and they were supported by a fleet of about 500 ships. The Persians had a smaller army of about 20,000 soldiers and they were supported by a fleet of about 200 ships. Alexander had the advantage of having the best army and the best navy, and he was able to defeat the Persians in battle.