After the death of Alexander in June 323 BC , Seleucus initially supported Perdiccas , the regent of Alexander 's empire , and was appointed Commander of the Companions and chiliarch at the Partition of Babylon in 323 BC .
After the death of Alexander in June 323 BC , Seleucus initially supported Perdiccas , the regent of Alexander 's empire , and was made Commander of the Companions ( the elite cavalry of Alexander ) at the Partition of Babylon in 323 BC .