The Greco-Persian War
The Persians conquered the kingdom of Lydia in Western Anatolia around 529 BC, the same year that Cyrus the Great died. His heir, Darius I, continued his predecesor's policies of toleration and justice. But this was a fateful chapter in the history of the Persian Empire, for this was the first time that the Persians had conquered a culturally Greek state. Darius followed the victory in Lydia by prosecuting war against the disorganized Greek city-states of Western Anatolia, which lay on the shores of the Aegean Sea. This outraged the newly minted city of Athens who in 499 BC sent aid to the Greek city-states of Anatolia. The Persians won anyway, but they were furious with Athens.
In 490 BC on Darius's orders, a massive navy transported the Persian army onto Greek soil. It is worth noting that while the Athenians called for help, no one responded, leaving Athens to face the onslaught alone. The Athenian war councils were hotly contested. A Persian army on Greek soil was an affront to the military Greeks, but a large group argued forcefully that the vaunted Persians were too much to cope with in open battle; they argued that Athens strong walls were their best defense. Nevertheless, more dynamic generals succeeded in carrying the day. They marched forth drawing up the Athenian army on the Plains of Marathon to face the most powerful army of the Middle East.
The Battle of Marathon was as unexpected as it was stunning; the Greek commanders unconventionally weakened the center of their army hoping it would bend but not break. In the event, this is exactly what happened, and though the Persians by all accounts outnumbered the Greeks, the reinforced Greek flanks clamped down, threatening to take the Persians from behind. The Persians army broke and fled to its ships. Darius was outraged when his army returned in defeat and swore vengeance against Athens. He immediately sent word throughout his empire to lay plans for a new expedition, one much larger and drawing on resources from all across the empire.
If Athenian support for the enemies of Darius in 499 BC was an affront to Persia, the Battle of Marathon in 490 BC was the first major defeat suffered by a Persian army. For Darius and the Persians it was no longer a matter of pride, but demonstrating to their vassals, that Greek victory was merely an unfortunate hiccup in Persia's continued supremacy. When he died in 486 BC, he was mourned throughout the empire, but the accesion of his son Xerxes made scarcely a ripple in Persia's plans for invasion. A massive army and navy were kept in close contact on the march to Greece, sometimes digging miles of canals to keep them united. In 480 BC, the extended preparations and engineering paid off as the Persians entered Greece. Exact numbers are always difficult to gauge from historical texts, but they may have been the largest army to invade Europe until D-Day in 1942.
On their march down through northern and central Greece, most kingdoms and city-states acknowledged Persian might by joining as vasals. Others remained neutral but hosted the Persians with the utmost tact; there was no hint of opposition until the Persians reached the narrow mountain defiles into southern Greece. There a Peloponnesian force lead by the Spartans joined with the Athenians to resist Persian rule and blockaded the massive Persian force at Thermopylae. The Persians were unable to benefit from their numerical superiority in the fortified mountain pass which allowed only a few soldiers to march abreast. With the aid of local supporters, however, they finally managed to slip a force through hidden mountain passes behind the Greeks.
This is where the legend of the 300 was born. Realizing they were about to be encircled, the Greeks could not retreat to safety without letting the main force bear down upon them. Therefore, 300 Spartan warriors volunteered to hold the pass while the rest of the Greeks fled south to fight again. The Spartans held their ground, a testament to their fierce military discipline, commitment to resisting the Persians on behalf of their freedom, and the awesome landscape that made Thermopylae a natural fortress; by the time the Persians had butchered the Spartans to the last man, the Greek army had successfully evaded them.
The massive Persian army next marched on Athens. They were stunned to find the city abandoned. In their rage, they sacked and burned Athens to the ground, then set off looking for the Greek armies, intent on victory. They managed to capture Greek prisoners who revealed that the army had fled aboard ship around the isle of Salamis; the massive Persian fleet was sent in hot pursuit. However, these prisoners were spies; playing a most dangerous game, the Greeks were desperate to engage the Persians in a place where the small number of powerful Greek ships could go one on one with the less powerful but far more numerous ships of Persia. When the lead ships of the Persian fleet poured through the Straits of Salamis, they were ambushed by the Athenian fleet.
The two navies crashed on a cold autumn morning, the Persians shocked by the sudden appearance of a fleet they believed to be miles away and headed in the opposite direction. The first ships of the Persian fleet were dispatched quickly, but soon the Greeks found themselves locked in the greatest naval battle of the Ancient Era. On the Greek side, Salamis gave the two navies limited space, allowing the stronger Greek ships to fight without being hopelessly surrounded by more numerous ships. Knowing that a decisive naval victory was the only way to prevent the Persians from ravaging Greece for years, they refused to retreat. The Persian admirals meanwhile still held a numerical advantage over the Greeks of more than two to one; while the narrow straits prevented them from using the fleet to their best ability, they also knew that the Greeks were unlikely to offer them a fair fight again. Neither side was willing to withdraw from their one best chance to win the war.
The battle raged all day. Only the fall of night could force the two determined fleets to disengage. As the sailors licked their wounds, the admirals of each fleet determined how much of their fleets had survived. According to the historical accounts, it was the Persians who first discovered that half their strength had been crushed at the Battle of Salamis, possibly the most important naval engagement in world history. The devastated Persian admirals ordered the fleet to slip away in the night. They survived but they never again chose to challenge the Greek fleet, giving the Greeks as stunning a victory as they had won in 490 BC at Marathon.
Without their navy to shield them, the Persian army faced the onset of winter with the daunting prospect of trying to feed the largest army ever assembled. Under other circumstances the Persian commanders would have ravaged Southern Greece to forage supplies. An unchallenged Athenian navy, however, was able to deposit Greek troops without warning anywhere they wished, and destroy the Persians one unit at a time. This forced the Persian commanders to accept that dispersing the army to live off the land would be suicidal. Therefore, the Persians reluctantly divided their army in half. One half consolidated itself safely inland to occupy the mainland, while the other half returned home to lessen the logistical nightmare of supplying so many troops. Some units sailed home aboard the remnants of the navy to bring news of the defeat home. However, most were forced to walk home exposed to the depredations of local kingdoms who were no longer awed by Persian invincibility. The news devastated the Persian court. Salamis marked the high point of Persian civilization. Occupying Greece and at the height of their power, never again would Persian fortunes rise so high.
That winter, in 479 BC, the army had settled into winter quarters. The Persians were therefore shocked when coalition forces led by Athens and Sparta drew up on the plains of Plataea opposite them. Sources are sometimes contradictory, but this was certainly the opportunity the Persians had been working for ever since they had entered Greece. With the odds in their favor, they deployed to meet the Greeks on the plains. The Greeks on the other hand had expected the Persians to fight on the defensive from their fortified camp, and seeing the Persians unexpectedly ready to give battle, withdrew to a more defensible position. This caused some of the coalition forces to be out of position when the Persians attacked. The Battle of Plataea was the largest land battle in world history to that point; a fitting climax to the war between the Persians and the Greeks – one civilization determined to reach beyond the Middle East and bring Europe into their orbit, the other determined to retain their freedom and traditions.
The Persians collided with the Greeks all along the line, and succeeded in smashing through the units which were out of position; they pushed through them and directly into the Spartan flank. There were stories of heroism on both sides across the battlefield, but the day was decided right there between the two greatest armies of their time, the Persians and the Spartans. And the Spartans carried the day. The Greeks sent the occupation force reeling back out of Greece; the largest Persian force in history faced a long march back to Persian lands, and they suffered even more grievously than the first army on their march home. Plataea ensured the security of Greece; never again would the Persians directly threaten Greece. These were the golden years of drama, poetry, politics, and philsophy in what is sometimes called the Hellenic Age of Ancient Greece.
The Interlude of "Peace"
However, the Persian Empire did not collapse; it's authority since the time of Cyrus had depended on its rule, not its army. However, the Persians still stung from the defeat, and while they never again attacked Greece, they used their vast wealth to destabalize the region. By supporting the Spartans in the Peloponnesian War (431 - 404 BC), Sparta was finally able to crush Athens. The bellicose Spartans in turn were so egotistical in victory, that they alienated their supporters, leaving Greece more divided than ever. It took almost 80 years, but by acting with great patience, Persia had ultimately undermined and destroyed the Greeks from within. It would have been better for them if they hadn't.
Their pettiness undermined much of the moral authority with which they ruled. Where the Battle of Salamis had not caused significant problems for the empire, their de facto victory over Greece in 404 BC came at a price. The Egyptians saw the Persian emperor's "victory" as a betrayal of Persian values; it's also likely that Egypt saw Persia's support of Sparta as a measure of the Persian army's weakness. Regardless, the Egyptians revolted in 404 BC and established their independence for several decades. In 380 BC, Persia's Indian provinces followed them; local dynasties achieved independence and Persian would never regain them. In 343 BC, Persia was finally able to reconquer Egypt. It was almost too late. With Greece mired in inter-city conflicts, it was a shadow of its former power, politically. It made Greece both vulnerable and bitterly hateful of the Persians; and while the Persians had no interest in renewing the Greek conflicts, the Greeks lacked only the means. And that was about to change.