Editing Seleucus I Nicator (section)

===Babylonian War===
{{Main|Babylonian War}}
[[File:LysimachusCoinWithHornedAlexander.jpg|thumb|left|250px|Coin of Lysimachus with an image of a horned Alexander the Great]]
Over the course of nine years (311–302 BC), while Antigonus was occupied in the west, Seleucus brought the whole eastern part of Alexander's empire as far as the [[Jaxartes]] and [[Indus River]]s under his authority.<ref name=EB1911>{{EB1911 |wstitle=Seleucid Dynasty |volume=24 |pages=603–604 |first=Edwyn Robert |last=Bevan |inline=1}}</ref>

In 311 BC Antigonus made peace with Cassander, Lysimachus and Ptolemy, which gave him an opportunity to deal with Seleucus.<ref name="G86">Grainger 1990, p. 86</ref> Antigonus' army had at least 80,000 soldiers. Even if he left half of his troops in the west, he would still have a numerical advantage over Seleucus. Seleucus may have received help from Cossaians, whose ancestors were the ancient [[Kassites]]. Antigonus had devastated their lands while fighting Eumenes. Seleucus perhaps recruited a portion of Archelaus' troops. When Antigonus finally invaded Babylon, Seleucus' army was much bigger than before. Many of his soldiers certainly hated Antigonus. The population of Babylon was also hostile. Seleucus, thus, did not need to garrison the area to keep the locals from revolting.<ref name="G89">Grainger 1990, pp. 89– 91</ref>

Little information is available about the conflict between Antigonus and Seleucus; only a very rudimentary Babylonian chronicle detailing the events of the war remains. The description of the year 310 BC has completely disappeared. It seems that Antigonus conquered Babylon. His plans were disturbed, however, by Ptolemy, who made a surprise attack in Cilicia.<ref name="G89" />

We do know that Seleucus defeated Antigonus in at least one decisive battle. This battle is only mentioned in ''Stratagems in War'' by [[Polyaenus]]. Polyaenus reports that the troops of Seleucus and Antigonus fought for a whole day, but when night came the battle was still undecided. The two forces agreed to rest for the night and continue in the morning. Antigonus' troops slept without their equipment. Seleucus ordered his forces to sleep and eat breakfast in battle formation. Shortly before dawn, Seleucus' troops attacked the forces of Antigonus, who were still without their weapons and in disarray and thus easily defeated. The historical accuracy of the story is questionable.<ref name="Grainger97">Grainger 1997, p. 54</ref><ref>{{cite web |author=Polyaenus |url=https://www.livius.org/cg-cm/chronicles/bchp-diadochi/polyaenus.html |title=The Babylonian war |publisher=Livius.org |access-date=2012-11-07 |archive-date=31 October 2012 |archive-url=https://web.archive.org/web/20121031180603/http://www.livius.org/cg-cm/chronicles/bchp-diadochi/polyaenus.html |url-status=dead }}</ref>

The Babylonian war finally ended in Seleucus' victory. Antigonus was forced to retreat west. Both sides fortified their borders. Antigonus built a series of fortresses along the [[Balikh River]] while Seleucus built a few cities, including [[Dura-Europos]] and [[Nisibis]].