After separate victories over rivals in A.D. 313, the Tetrarchy (rule of four) ended, and the Roman Empire was again ruled by two emperors - Constantine the Great and Licinius. Licinius celebrated his success with a massacre of any possible rivals. He executed the daughter and the widow of Diocletian, along with the son of his former friend Galerius. An uneasy truce existed between the two, until Licinius came to suspect Christians were conspiring against him. He expelled all Christian officers in his army, and had certain bishops he thought disloyal executed. This provoked the final showdown between the two emperors. In A.D. 324, Constantine defeated Licinius, and later executed him.