After the embarrassment of Marathon, the Persians returned with a vengeance in their massive second invasion of Greece. This time advancing via the Black Sea straits to avoid the complications of an amphibious landing, they marched into Greece from the north through Macedonia. To meet the advance, the Greeks first sent a force into Thessaly to defend the mountain passes. Finding this position untenable, they then retreated south to Thermopylae, a narrow pass between the cliffs and the sea which at that time may have been no more than fifteen meters wide (see Herodotus VII, pg. 176). The defense of this pass is perhaps the most famous action of any Hoplite army, immortalized in history and in a very-slightly exaggerated Hollywood film. Hollywood did get the most important parts right, however – The Greeks chose to stand at this pass against the Persians in close order at the narrowest part, beating back waves of Persian troops. Here they doubtless fought in the phalanx as it exists in common perception, an interlocked shield wall through which the Hoplites stabbed repeatedly at any enemy hapless enough to venture within the range of their eight-foot spears (see Diodorus XI, pg. 7). Reportedly, the Persians were slaughtered during the first two days of battle, as the Persian King, Xerxes, sent his infantry to conduct repeated frontal assaults against the Greek line. What followed, according to Herodotus, was a flanking movement by the Persians to get around the pass with the aid of a Greek traitor who showed them an alternate route. Thus encircled, the Greek defenders were destroyed to a man. What Thermopylae proved, however, was that Hoplites remained more than a match for the light-armed Persians when they came to grips, destroying them by the thousands when the King’s forces attempted to breach their tightly-packed, well-armored line.