In the early 1970s the Sultan of Oman was fighting the Dhofar Rebellion with British support. As a result of Sultan Qaboos's diplomatic initiatives, the Shah sent a brigade of troops numbering 1,200 and with its own helicopters to assist the Sultan's Armed Forces in 1973. The Iranian brigade first secured the Salalah-Thumrait road. In 1974, the Iranian contribution was expanded into the Imperial Iranian Task Force, numbering 4,000. They attempted to establish another interdiction line, codenamed the "Damavand Line", running from "Manston", a few miles east of Sarfait, to the coast near the border with South Yemen (the PDRY). Heavy rebel opposition, which included artillery fire from within South Yemen, thwarted this aim for several months. Eventually, the town of Rahkyut, which the PFLO had long maintained as the capital of their liberated territory, fell to the Iranian task force. The IITF remained in Oman in December 1975, then at a strength of 3,000.