As the Persians bore down on Greece, the city-states of the resistance decided to use their army to block the pass of Thermopylae. At the same time, their fleet would confront the Persian navy in the nearby waters off Artemisium. Before the Greek forces could set out, disaster struck: the Olympic and Carneian religious festivals imposed a taboo on war-making. At this moment of supreme crisis, King Leonidas of Sparta led out an advance guard to hold Thermopylae. In two days of intense fighting on land and sea, the Greeks managed to stop the Persian advance.