In 1883, the Dutch colonial government signed a peace treaty with the Acehnese guerrillas. That same year Umar joined them as an undercover operative over Dhien's complaints, working his way up through the colonial military's ranks. After war broke out again in 1884, Umar worked to stop the Acehnese people's struggle. For his service, on January 1, 1894 Umar was given the title "Johan Pahlawan" and control of a legion of 250 fully armed soldiers. Eventually, Umar was given control of 120 more troops as well as 17 lieutenants.