Alerted to the advance, Petronius again marched south and managed to reach Qasr Ibrim and bolster its defences before the invading Kushites arrived. Although the ancient sources give no description of the ensuing battle, we know that at some point the Kushites sent ambassadors to negotiate a peace settlement with Petronius. By the end of the second campaign, however, Petronius was in no mood to deal further with the Kushites.[49]:149 The Kushites succeeded in negotiating a peace treaty on favourable terms[1] and trade between the two nations increased.[49]:149 Some historians like Theodore Mommsen wrote that during Augustus times Nubia was a possible client state of the Roman Empire.