He was born in Baghdad and graduated from the Iraqi military academy. By 1955 he was a high-ranking military officer and by 1957 he was part of a group in the army opposed to the monarchy. He deposed the Iraqi monarchy on July 14, 1958 in a coup in which many royal family members and politicians were killed, and was himself deposed by Abdul Salam Arif on February 8, 1963. During his time in power he was prime minister of Iraq. He ended the short-lived union with Jordan. During this period there was a major debate over whether Iraq should join the United Arab Republic instead. Qassim was the victim of an assassination attempt in 1959 in which Saddam Hussein was involved. The attempt was carried out by pan-Arabists who wanted Iraq to join the UAR. Qassim either wanted Iraq to remain independent or join at a later date. This did not satisfy the Egyptian president, Gamal Abdul Nasser, making foreign relations difficult for the Iraqi government. Qassim also had to deal with rebellions in Mosul in 1959 and in the Khurdish areas in 1961. He was killed in Baghdad soon after being deposed.