The struggle between the proponents and opponents of Arab unity was not only ideological in nature. Through it, for instance, ran the concerns of Shiite Arabs and Kurds, who were in a politically subordinate position in Iraq and feared that a unified Arab state would be dominated even more strongly by Sunni Arabs. Partly for this reason, many Shiite Arabs and Kurds supported the Iraqi Communist Party (ICP), which opposed Arab nationalism because of its anti-Communist character.
In Iraq, advocates of Arab unity were found chiefly among the Sunni Arabs. In March 1959, things reached the point of a revolt in Mosul, organized by the Baath Party, which was bloodily repressed by the army, with the support of members of the Communist militia. The ruling regime soon thereafter had the Communist militias disbanded, out of fear of the growing influence of the ICP.
Two years later (1961) the regime came under pressure also from Kurdish nationalists. After previous concessions regarding the fulfilment of their national aspirations were not met, the Kurdish peshmerga took up arms again, under the leadership of their charismatic leader Mala (Mullah) Mustafa Barzani, who had earlier returned from exile. In a short time they had conquered almost the entire Kurdish region, from Zakho to Sulaymaniya. The conflict dragged on until February 1964, when Barzani and Baghdad signed a cease-fire agreement.