The Pax Romana began when Octavian (Augustus) defeated Mark Antony and Cleopatra in the Battle of Actium on 2 September 31 BC and became Roman emperor. He became princeps, or "first citizen". Lacking a good precedent of successful one-man rule, Augustus created a junta of the greatest military magnates and stood as the front man. By binding together these leading magnates in a coalition, he eliminated the prospect of civil war. The Pax Romana was not immediate, despite the end of the civil wars, because fighting continued in Hispania and in the Alps. Nevertheless, Augustus closed the Gates of Janus (a ceremony indicating that Rome was at peace) three times, first in 29 BC and again in 25 BC. The third closure is undocumented, but Inez Scott Ryberg (1949) and Gaius Stern (2006) have persuasively dated the third closure to 13 BC with the commissioning of the Ara Pacis. At the time of the Ludi Saeculares in 17 BC the Concept of Peace was publicized, and in 13 BC was proclaimed when Augustus and Agrippa jointly returned from pacifying the provinces. The order to construct the Ara Pacis was no doubt part of this announcement.