 Complete the following phrase:  Thermopylae was the only gateway into Greece for the Persian army, and presented the perfect choke point  a narrow pass bordered by a huge mountain wall on one side and a cliff drop-off to the sea on the other. This area decreased the Persians advantage of having large numbers. Delaying the Persian advance here would give the Greek allies enough time to ready a larger, main force to defend against the Persians. The battle takes place simultaneously with the sea battle at 