The rest of Persia, the territory that makes up the modern nations of Iran, Azerbaijan, and Afghanistan, was conquered by two separate military campaigns. The first was a defensive action by the Arab commanders in Iraq, while the second invasion came from the sea, a first for the Islamic State at Medina.
The Persian king, Yazdgerd, was down but not out. Pushed to his eastern margins, he asked the Turkic Khan of Ferghana to assist him in winning back his homeland. Around 642, he put out a call to all remaining loyal cities and officers to gather at a place called Nahavand. From there, they’d move toward Iraq, probably attacking the Arab garrison town of Basra, which was not walled.
But you can’t mass an army of tens of thousands without someone noticing. Arab scouts brought the news back to Basra, then to Medina. Caliph Umar and his top advisers considered what to do. Some argued that a massive army should be raised from Arabia, Iraq, and Syria. Ali argued that the forces in Iraq should be sufficient if they moved quickly before the Persians were ready. So that order went out: mobilize as soon as possible, and move toward Nahavand to dispatch the Persians there.
At Nahavand, the Persians were camped between a ridge of hills and a stream. When they suddenly had to create a defensive formation, they spread caltrops—basically, the shape that we know as the children’s toy “jacks”—along the stream bank. These metal spikes would lame any horses who stepped on them. The stream, caltrops, and hills made a natural fortress during which the Persians were safe for several days of fighting.
The Muslim commander took a break from large assaults to study the situation. During this break, he had his army circulate a rumor that Caliph Umar had died. He waited for spies to carry the rumor back to the Persian camp. A week passed. Then the Muslims began an orderly retreat that would be consistent with a leadership crisis in Medina, but a large unit of cavalry also slipped behind a hill to reposition near the back of the Persian camp. The Persians took the bait and moved out of the safety of their camp. The Muslims then turned and began an open battle with many deaths. The cavalry unit started attacking the back of the Persian lines.
The battle turned quickly when both commanders were killed. In the Arab army, there was an experienced command structure of officers who had fought in the other major battles. Someone quickly took over. But the long war with Rome and their major loss at Qadisiyah had deprived the Persian army of experienced officers. The masses gathered at Nahavand were mostly recruits or men from distant places with language barriers. When the commander died, nobody took over, and the men turned to flee. Especially with a cavalry unit attacking at the back, this flight sealed their defeat. It was an unmitigated disaster for Persia and ensured that no central army could be massed again for a long time to come.
A separate Arab force had moved out of eastern Arabia across the Persian Gulf around 639. Umar was very uncomfortable with any military operations in ships, but the Arabs along the coast had always been going to sea (recall the Bronze Age shipping between Sumer and India). They were the men of modern Bahrain, Kuwait and Oman. In 639, they established an Arab base on an island and began the invasion of the Persian homeland, Fars. They had begun draining off some of Yazdgerd’s war reserves by making him defend Fars.
After the major victory at Nahavand, the East Arabians could establish a permanent base, a misr, on the Persian shore. Yazdgerd was in the city of Istakhar. Fars was mountainous, an easy place to defend, a hard place to attack. But without a major central force to come rescue them, each city had to make its own choices. Some surrendered, others fought as they could. Much of Iran lay open now, and some of the Arab armies went far east and north, receiving terms and tribute from places as far as the edges we now call Afghanistan, Azerbaijan, and Pakistan.
It took combined Arab forces to dislodge Yazdgerd from Istakhar. The governor of Basra had improved his town with irrigation canals, and more and more people were settling there. Basra could now send most of its fighting men into Iran. The city of Jur was impregnable until someone noticed a dog running toward the city. He followed the dog who knew the way through a pass and up to a back gate. With that knowledge, the Arabs made short work of Jur.
Istakhar held out longest, and it may have surrendered for a short time, then rebelled. Its walls were pounded by catapults, then the city was invaded for bloody urban fighting. When the Arab victory was assured, the commander ordered a mass execution of the Persian nobles who had gathered there. Tens of thousands were executed, and the fire temples were destroyed. Sacred fires were put out, walls torn down, and votive riches seized. It is the only city that is recorded as being razed.
Yazdgerd escaped to the border of the Turkic lands. The Arabs pursued him, forcing cities along the way to surrender as their nobles fled. They went into all of the eastern and northern provinces until the Islamic State controlled modern Pakistan, Azerbaijan, and some of Afghanistan, in addition to Iran. One of the outlying cities, Zaranj, agreed to colorful terms: annually one million dirhams of silver and one thousand slave boys each carrying a golden cup (Kennedy, 187). The outlying city of Merv marked the extent of the Muslim advance.
Yazdgerd was running ahead of them all this time. The status of a fugitive king is different from a retreating one; when the king is a fugitive, he is toxic to be near. The king was passed along from one town to another, always trying to form alliances to turn things around. He ended up in Merv, too. Chased out of the town by the governor’s fear when he heard of the Muslim advance, he could have gone into Turkic or even Chinese lands. Instead, he turned back to go quietly toward central Iran and attempt a rebellion. When he took shelter in a mill, the local ruler ordered the miller to kill him. Local Nestorian monks found his body and reverently prepared it for burial.
Yazdgerd’s final end didn’t come until 651, well into the reign of the next Caliph. The Sassanid dynasty was over, and with it, Persia as it had been. During the coming Muslim years, Persia would struggle along as small principalities fighting each other and trying to stave off eastern invasions. It would not be a unified country again until 1501.
- Great Arab Conquests, by Hugh Kennedy
- The War of the Three Gods: Romans, Persians, and the Rise of Islam, by Peter Crawford.