In 297 Diocletian, augustus since 284, campaigned in Egypt to suppress the revolt of the usurper Domitius Domitianus. After a long siege, Diocletian captured Alexandria and executed Domitianus's successor Aurelius Achilleus in 298. In 302 the emperor returned to the city and inaugurated a state grain supply. The dedication of the column monument and its statue of Diocletian, describes Diocletian as polioúchos (). In the fourth century AD this designation also applied to Serapis, the male counterpart of Isis in the pantheon instituted by the Hellenistic rulers of Egypt, the Ptolemies. The sanctuary complex dedicated to Serapis in which the column was originally erected, the Serapeum, was built under King Ptolemy III Euergetes in the third century BC and probably rebuilt in the era of the second century AD emperor Hadrian after sustaining damage in the Kitos Wars; in the later fourth century AD it was considered by Ammianus Marcellinus a marvel rivalled only by Rome's sanctuary to Jupiter Optimus Maximus on the Capitoline Hill, the Capitolium.