Augustus commanded Gallus to undertake a military expedition to Arabia Felix in 26 BC, where he was to either conclude treaties making the Arabian people foederati (i.e. client states), or to subdue them if they resisted. According to Theodor Mommsen, Aelius Gallus sailed with 10,000 legionaries from Egypt and landed at Leuce Kome, a trading port of the Nabateans in the northwestern Arabian coast. Gallus' subsequent movements relied on a Nabataean guide called Syllaeus, who proved to be untrustworthy. As a result of Syllaeus' misdirections, the army took six months to reach Ma'rib, the Sabaean capital.