May 28, 2013 · Sparta, under Cleomenes (c. 520-490 BCE), overthrew the tyrants of Athens but the resulting democracy put a stop to any Spartan ambitions in the city. Sparta was, however, an ally with Athens in the defence of Greece against the invasion of Persian king Xerxes, and fought with distinction at Thermopylae in 480 BCE and at Plataea one year later.