The Battle of Marathon in 490 B.C was made one of the biggest turning point in history. The Persian army wanted to expand on there territory so they wanted to take over the Athens.
The Athens, were outnumbered, and needed the help of Sparta's military base. Time was very short for them, so the Athenian sent Phidippides (a professional runner) to Sparta asking for help. Phidippides ran 140miles to Sparta in about 36 hours. When he got there Sparta agreed to help but said they couldn't fight until the moon was full.
This left the Athenians alone to fight the Persian Army. Phidippides ran back to Athens with the disappointing news. The Athenian Army were still outnumbered but they made a suprise offensive thrust and at the time looked suicidal. But at the end of the day, 6400 Persian bodies were dead while only 192 Athenians were killed.