The establishment of Arab Sunni domination in Iraq led to significant unrest among Assyrian, Yazidi, and Shi'a communities, which were met with harsh suppression. In 1936, Iraq experienced its first military coup, led by Bakr Sidqi, who replaced the acting Prime Minister with an associate. This event initiated a period of political instability characterized by multiple coups, culminating in 1941.

World War II saw further turmoil in Iraq. In 1941, the regime of Regent 'Abd al-Ilah was overthrown by the Golden Square officers, led by Rashid Ali. This pro-Nazi government was short-lived, defeated in May 1941 by Allied forces, with assistance from local Assyrian and Kurdish groups, in the Anglo-Iraqi War. Post-war, Iraq served as a strategic base for Allied operations against the Vichy-French in Syria and supported the Anglo-Soviet invasion of Iran.

Iraq became a member of the United Nations and a founding member of the Arab League in 1945. That same year, Kurdish leader Mustafa Barzani initiated a rebellion against Baghdad's central government, leading to his eventual exile in the Soviet Union after the uprising's failure.

In 1948, Iraq witnessed the Al-Wathbah uprising, a series of violent protests in Baghdad with partial communist backing, against the government's treaty with Britain. The uprising, continuing into spring, was halted by the imposition of martial law as Iraq joined the unsuccessful Arab-Israeli War.

The Arab-Hāshimite Union was proposed in 1958 by King Hussein of Jordan and 'Abd al-Ilāh, a response to the Egyptian-Syrian union. Iraqi Prime Minister Nuri as-Said envisioned including Kuwait in this union. However, discussions with Kuwait's ruler Shaykh 'Abd-Allāh as-Salīm led to a conflict with Britain, which opposed Kuwaiti independence. The Iraqi monarchy, increasingly isolated, relied on heightened political oppression under Nuri as-Said to quell rising discontent.