Thus, on the morning of 13 September, the tenth day of the march from Caputvada, the Roman army approached Ad Decimum. There Gelimer planned to ambush and encircle them, using a force under his brother Ammatas to block their advance and engage them, while 2,000 men under his nephew Gibamund would attack their left flank, and Gelimer himself with the main army would attack from the rear and completely annihilate the Roman army. In the event, the three forces failed to synchronize exactly: Ammatas arrived early and was killed as he attempted a reconnaissance with a small force by the Roman vanguard, while Gibamund's force was intercepted by the Hunnic flank guard and was utterly destroyed. Unaware of all this, Gelimer marched up with the main army and scattered the Roman advance forces present at Ad Decimum. Victory might have been his, but he then came upon his dead brother's body, and apparently forgot all about the battle. This gave Belisarius the time to rally his troops, come up with his main cavalry force and defeat the disorganized Vandals. Gelimer with the remainder of his forces fled westwards to Numidia. The Battle of Ad Decimum ended in a crushing Roman victory, and Carthage lay open and undefended before Belisarius.