First Siege of Babylon (311 BC)

After the partition of Babylon. Seleucus was appointed as the satrap of Babylon until he was forced to leave, fearing Antigonus increasing power in 315 BC and took refuge at Ptolemy's court, where he remained until he and Ptolemy defeated Antigonus's son Demetrius at Gaza in 312 BC, after which Ptolemy delivered to him 200 cavalry and 800 foot soldiers, and begun his advance towards his old satrapy of Babylon.

Seleucus now march towards Harran (also known as Carrhae) where he found around 1000 veteran troops, (probably a portion of the Silver Shields captured at Gabiene) who joined him, then he proceeded towards Babylon, which he reach in may, the people welcomed him, as he was well remembered by them, but a small force loyal to Antigonus entrenched themselves in the citadel of the palace.

Seleucus decided to lay siege on the citadel, but eager to avoid casualties, he decided to cut the water supply to the city and began to build a dam on the river Euphrates, which passed between the citadel walls, until it created an artificial lake on the hill, but as the citadel continue to resist his attempts, he ordered the dam to be suddenly broken and in the ensuing downstream flood the walls of the citadel were destroyed and the garrison surrendered after token resistance.

Seleucus became ruler of Babylon again, however, Antigonus had enough power to recapture the city at any moment, and one of his generals, Nicanor was already on the way, this episode marks the start of the Babylonian War.

• https://www.livius.org/sources/content/diodorus/the-beginning-of-the-babylonian-war/
• Chronicle of the Diadochi, rev., iv.7'.
• https://www.livius.org/sources/content/mesopotamian-chronicles-content/bchp-3-diadochi-chronicle/
• Diodorus Siculus, World History, 19.90-93