Expansion
Cyrus’ first step was to consolidate his power over tribes on the Iranian plateau. Croesus, The King of Lydia, a region in Asia Minor, grew his domains at the expense of the Medes when he heard about the defeat of Astyages. Cyrus marched against Croesus and defeated the Lydian army; he captured the enemy capital, Sardis in 547 BC and King Croesus apparently died in the fighting. Other ancient sources suggest the king survived and was well treated by Cyrus.
After capturing much of Asia Minor in the aftermath of his triumph over Lydia, Cyrus turned his attention east to ensure his fledgling empire’s borders were safe from invasion by nomadic tribes. During this period, he conquered territories such as Soghdiana, Parthia, and Hyrcania right up to the River Jaxartes which flows into the Aral Sea.
According to Homa Katouzian in The Persians: Ancient, Medieval and Modern Iran, Cyrus was responsible for introducing agriculture into these regions, and he also created fortress towns. Perhaps the most famous of these is Samarkand in Uzbekistan. The purpose of the fortresses was to protect the north-eastern region from incursions by the nomads of Central Asia.
The Fall of Babylon
During the sixth century BC, Babylon was considered by many to be the greatest city in the ancient world. However, Cyrus ultimately conquered it with relative ease. After his general, Harpagus had conquered Lycia, Cicilia, and Phoenicia by 542 BC, he was ordered back to Persia having completed his mission. However, Cyrus had already set his sights on the capture of Babylon.
By 540 BC, the Persians had captured Elam, and its capital Susa, and moved on towards Babylon. The Battle of Opis took place in either 540 or 539 BC and featured the Persian army under Cyrus against the Babylonian army under King Nabonidus. We get our information from the aforementioned Nabonidus Chronicle, but it doesn’t give much detail about the Battle of Opis.
All we know is that the Babylonians were defeated and possibly routed. There is some confusion over the translation of the chronicle which says there was a ‘massacre’ of ‘the people of Akkad.’ Whether this refers to the citizens of Opis or the fleeing Babylonian army is unclear.
Opis was a pivotal battle as it enabled the Persians to march towards the city of Babylon with minimal resistance. A few days after the battle, Cyrus was able to take the city of Sippar peacefully. King Nabonidus was hiding in Sippar and had to flee to Babylon where he had apparently not been in years. His time was up when the Persian General Gubaru entered Babylon itself; again without any resistance, and detained the king. Cyrus arrived a few weeks later.
Cyrus was an incredibly active ruler and had several different capitals during his reign as leader of the Achaemenid Empire. In the beginning, his capital was Anshan with Ecbatana as the ‘second’ capital once he conquered Media. He was also officially invested as king in Babylon, but ultimately, Cyrus created his new capital at Pasargadae which possibly meant ‘camp of the Persians.’ Construction of the city began in 546 BC but was not completed at the time of his death. Pasargadae remained the empire’s capital until Darius the Great moved it to Persepolis.