Throughout his term of leadership, the Iraqi Regional Branch expanded its membership and became a leading party in Iraq's political landscape.

Following the 14 July Revolution of 1958 which toppled the monarchy, al-Rikabi was appointed Minister of Development in Abd al-Karim Qasim's unity government.

Al-Rikabi and the Iraqi Regional Branch of the Ba'ath Party came to the conclusion that the only way to expedite Iraq's entry into the United Arab Republic was to assassinate Qasim.

He agreed with Abdullah Rimawi's observation that the National Command, the ruling organ of the Ba'ath Party, had deviated from Ba'athist thought.

From then on al-Rikabi was a prominent Nasserite, active first in Rimawi's Revolutionary Ba'ath Command and then in Arif's Arab Socialist Union.

[3][4][5][1] The party initially consisted of a majority of Shia Muslims, as al-Rikabi recruited supporters mainly from his friends and family, but it slowly became Sunni-dominated.

This in turn led to a clampdown on Arab nationalist activities, which included the Iraqi Regional Branch of the Ba'ath Party.

[12] The failure of both Arif and the 1959 Mosul Uprising by the pro-UAR colonel Abd al-Wahab al-Shawaf led al-Rikabi and the Iraqi Regional Branch of the Ba'ath Party to conclude that the only way to secure Arab nationalist rule was by assassinating Qasim.

[14] The Ba'ath Party's organisation was weakened following the failed assassination attempt,[15] and on 29 November 1959 the Regional Command was dissolved.

On 24 June he held a press conference in Beirut where he stated that the Iraqi Regional Branch of the Ba'ath Party had broken its relations with the National Command.

Al-Rikabi also believed that the National Command had lost faith in its Ba'athist beliefs, while the Iraqi Regional Branch needed it the most.

The reconstituted Iraqi Regional Command passed a resolution on 2 February 1962 which expelled al-Rikabi from the organisation and appointed Talib Hussein ash-Shabibi as secretary general.

Attacks on al-Rikabi continued, and the Iraqi Regional Congress in July 1960 called the National Command to initiate an investigation against him.