On 18 October 1749, the ruler of Amabi informed the Dutch of a large army assembling. Da Costa wanted to force Sombai to swear fealty to him, with the aid of Portuguese-aligned rulers in the area in addition to men from Larantuka. The Amarassi "raja", one of the rulers aligned with da Costa, sent an envoy to attempt to convince the Kupang "raja" and the Dutch to remain neutral in the conflict. Dutch accounts estimated "tens of thousands" of enemy forces, ranging from 20,000 to 50,000, although this figure was likely an exaggeration as Timor's population then was far below half a million. Some of the men were from native leaders who had been forced to join the army, and several leaders had been killed by da Costa as he suspected them of defecting to the Dutch. According to oral traditions, the army was assembled at Nunuhenu, in Ambeno, before it marched towards Kupang. Da Costa was not supported by the Portuguese authorities, and also did not hold full control over the Topass – with the competing de Hornay family not participating in the battle. Aside from allies, which did not participate in the initial fighting, there were around 500 Dutch soldiers – a sergeant and two corporals, 20 Europeans, 130 Mardijkers, 240 from Sabu, 60 from Solor, and 30 from Rote, in addition to volunteers from the company. All were provided firearms. In addition, there were additional soldiers who were garrisoned in Kupang's fortress and town. The Dutch force was commanded by Ensign Christoffel Lipp, while the Mardijkers were commanded by Frans Mone Kana. Prior to the battle, large parts of Kupang's population fled the town, fearing the approaching army, with Dutch accounts noting the local VOC commander needing to convince their native allies into fighting. The men from Rote and Sabu were also initially demoralized, with VOC having to give promises and sinking the ships before they could be used to flee. Da Costa's army camped at Penfui, a hillside to the east of Kupang, and constructed stone and earthen forts there. On Sunday morning of 9 November 1749, the Dutch forces departed Kupang to engage the encampment. Upon encountering the incoming Dutch forces, the Amarasi, who was assigned to the frontmost fortification, sent the Dutch an envoy saying that they "could from now on be called friends of the Dutch" and the Amarasi fled the battlefield, without pursuit from the Dutch.