In order to support a royal title for Caesar a rumor was spread in the lead up to the planned invasion. It alleged that it had been prophesied that only a Roman king could defeat Parthia.[1][2] As Caesar's greatest internal opposition came from those that believed he wanted royal power, this strengthened the conspiracy against him.[25] It has also been proposed that Caesar's opposition would be fearful of him returning victorious from his campaign and more popular than ever.[4][26] The assassination occurred on 15 March 44 BC on the day the senate was to debate granting Caesar the title of king for the war with Parthia.[10] However, some of the aspects of Caesar's planned kingship may have been invented after the assassination in order to justify the act.[6] The relationship between the planned Parthian war and his death, if any, is unknown.[5][27]