what event caused the greek city- states to put aside their differences.

The event that caused the Greek city-states to put aside their differences was the Persian invasion of Greece, which began in 480 BCE. To better understand this event and its impact on the city-states, we can look at the following steps:

1. Background: Prior to the Persian invasion, the Greek city-states were constantly competing and often at war with each other. The two major rival city-states were Athens and Sparta, which had different political systems and interests.

2. Persian Empire Expansion: The Persian Empire, under the leadership of King Darius I and later his son Xerxes, aimed to expand their empire by conquering Greece. In 490 BCE, Darius I led an unsuccessful invasion of Greece, which was repelled at the Battle of Marathon.

3. Gathering of Greek Allies: Fearful of another Persian invasion, many Greek city-states realized the importance of uniting against the common enemy. Athens, known for its naval power, took the lead in forming alliances with other city-states and created the Delian League, a defensive coalition against the Persian threat.

4. Spartan Leadership: Despite their differences, Athens and Sparta put aside their rivalry to work together against the Persians. Sparta, renowned for its military prowess, took charge of the land forces, while Athens led the naval forces. This cooperation reflected their shared goal of defending Greece's independence.

5. Battle of Thermopylae: In 480 BCE, the Persian forces, led by Xerxes, launched a massive invasion of Greece. At the Battle of Thermopylae, a small Spartan-led force held off the Persian army for several days, allowing the city-states more time to prepare.

6. Victory at Salamis: The decisive moment came at the Battle of Salamis, where the Athenian navy, along with the combined Greek city-state naval forces, inflicted a significant defeat on the Persian fleet. This victory bolstered Greek morale and significantly weakened the Persian forces.

7. Uniting for the Greater Good: The successful defense against the Persian invasion highlighted the importance of unity among the Greek city-states. They realized that by putting aside their differences and working together, they could overcome external threats and safeguard their independence.

In conclusion, it was the Persian invasion of Greece and the need for collective defense that prompted the Greek city-states to set aside their differences and form alliances. This unity was instrumental in their victory over the Persians and ultimately shaped the course of Greek history.

There were several events -- but check to see if your text mentions the Persian Wars.

Also -- the city-states put aside their differences for the Olympics.