The second triumvirate was formed in 43 BC by Octavian, Mark Antony, and Lepidus in order to consolidate power and defeat the republican forces of Brutus and Cassius. They engaged in brutal proscriptions that killed thousands, including Cicero. They defeated Brutus and Cassius at the battle of Philippi in 42 BC, effectively ending the republic. However, tensions grew between Octavian and Antony over the next several years as Antony allied with Cleopatra in Egypt, threatening Octavian's power and leading to war between the two rivals in 31 BC.