Chinese rebels were present in Central Java, particularly around Tanjung (Welahan), Pati, Grobogan, and Kaliwungu. In May 1741 Juwana was captured by the Chinese. The Javanese at first sided with the Dutch and reinforced Demak on 10 June 1741. Two days later, a detachment of Javanese forces together with the VOC forces of Europeans, Balinese and Buginese in Semarang to defend Tugu, west of Semarang. The Chinese rebel lured them into their main forces's position in Mount Bergota through narrow road and ambushed them. The allied forces were dispersed and ran as fast as they could back to Semarang. The Chinese pursued them but were repulsed by Dutch cannons in the fortress. Semarang was seized by panic. By July 1741, the Chinese occupied Kaligawe, south of Semarang, Rembang, and besieged Jepara. This is the most dangerous time for the VOC. Military superiority would enable the VOC to hold Semarang without any support from Mataram forces, but it would mean nothing since a turbulent interior would disrupt trade and therefore profit, the VOC's main objective. One VOC high official, Abraham Roos, suggested that the VOC assumed royal function in Java by denying Pakubuwana II's "legitimacy" and asking the regents to take an oath of loyalty to the VOC's sovereignty. This was turned down by the Council of Indies (Raad van Indie) in Batavia, since even if the VOC managed to conquer the coast, it would not be strong enough to conquer the mountainous interior of Java, which do not provide much level plain required by Western method of warfare. Therefore, the Dutch East India Company must support its superior but inadequate military by picking the right allies. One such ally had presented itself, that is Cakraningkrat IV of Madura who could be relied on to hold the eastern coast against the Chinese, but the interior of Eastern and Central Java was beyond the reach of this quarrelsome prince. Therefore, the VOC had no choice but to side with Pakubuwana II. The VOC's dire situation after the Battle of Tugu in July 1741 did not escape the king's attention, but – like Amangkurat II – he avoided any open breach with the VOC since his own kraton was not lacking of factions against him. He ordered Patih Natakusuma to do all the dirty work, such as ordering the Arch-Regent (Adipati) of Jipang (Bojonegoro), one Tumenggung Mataun, to join the Chinese. In September