A month after his graduation from the academy, the Dutch began a military offensive codenamed Operation Kraai. As a second lieutenant, Sayidiman returned to his post as a platoon commander inside the Nasuhi Battalion. Sayidiman did not hold his old post for a long period as in December 1949 he was transferred to command the 1st company inside the 13th Brigade in an acting capacity. After the peace treaty between Indonesia and the Dutch was signed, Sayidiman was promoted to first lieutenant on 12 April 1950 and became the company's commander. Following a reorganization inside the 13th Brigade, Sayidiman was transferred to the 2nd Company in the battalion in June 1950, where he fought against the Darul Islam rebels. According to Salim Said, a lecturer in the Indonesian Defence University, Sayidiman initially wanted to attend military schools abroad after the peace treaty was made but changed his mind because he felt that he "owed a debt of gratitude to the people".