T. G. Longstaff made the first climbing reconnaissance of Trisul, in September 1905, focussing on the western and southern sides. He returned in 1907 with two other Britons, three Alpine guides, and a number of Gurkhas. They ascended through the Rishiganga valley, to the north of the peak, onto the Trisul Glacier, which lies on the east side. From there they climbed the northeast flank to the north ridge, reaching the summit on 12 June. At the time Trisul was probably the highest mountain to have been climbed. The climb was noted also for the first use of supplementary oxygen in a major climb. During the 1950s Harold Williams led Indian Army expeditions to the summit.