 Along with Hoesni Thamrin, and Amir Sjarifoeddin, Tjokrosujoso formed the Indonesian National Political Assembly (PPKI), a united front consisting of all political parties, groups, and social organizations advocating the country's independence.The PPKI offered the Dutch colonial authorities full support in their defense against the Japanese if they were granted the right to establish a parliament under the rule of the Queen of the Netherlands.The Dutch refused the offer.