 In 1913, Imam Salim ibn Rashid al-Kharusi instigated an anti-Muscat rebellion that lasted until 1920 when the Imamate established peace with the Sultanate through the signing of Treaty of Seeb.The treaty resulted in a "de facto" split between Oman and Muscat, wherein the interior part (Oman) was ruled by the Imamate and the coastal part (Muscat) was ruled by the Sultanate.Iraq Petroleum Company, which signed an oil concession with the Sultan of Muscat in 1937, deduced that oil was very likely to exist in the interior regions of Oman.