He advanced on land with about 18,000 men himself. Soon he would encounter Gelimer at Ad Decimum. The Byzantines were located in between the Vandal forces in the north and the south. Gelimer needed a victory at Ad Decimum to unite his forces. Numbering about 10,000-12,000, the Vandals were outnumbered. The valley in which the ambush was to take place was narrow, and as two of the three roads to Carthage became one in the valley, it seemed like a great spot for an ambush to Gelimer. Ammatus, with 6,000-7,000 men, was ordered to block the northern exit and attack the Byzantines head-on, then drive them further back into the valley and cause disorder.< Meanwhile, 5,000-6,000 Vandals under Gelimer were already advancing towards Belisarius from the south as the earlier clash showed; these would be in the near vicinity when Belisarius entered the valley and attacked them from behind after all Byzantines had moved into the valley. Brogna states that this plan was doomed to fail, as coordination over dozens of miles was needed, however, Hughes disagrees and calls the plan “elegant and simple”, but does state that the plan relied too much on hard to pull off timing and synchronization. The battle consisted of four separate stages. Four miles (6.5 km) from Ad Decimum, Belisarius found an ideal spot to camp. Leaving the infantry behind to build a camp, he rode out with his cavalry to meet the Vandals who he suspected were nearby. This way he left his infantry, baggage, and wife in a secure position. Unlike the large infantry force, he would easily be able to control this small force of cavalry, which was the main strength of the Byzantine army. When Belisarius arrived at the battlefield, the first three stages of the battle had already taken place. The Byzantines sent ahead to scout and the Huns guarding the flank had routed the numerically superior forces opposing them. Before Belisarius arrived at the field of battle, he encountered some units routed by Gelimer's army, who informed him of the situation in the third stage, when Gelimer himself arrived. When Belisarius arrived, Gelimer had seen that his brother Ammatus was killed in combat. Mourning, he remained idle and allowed Belisarius to attack his force while it was in a disorganized state in the fourth and last stage of the battle.