The withdrawal of Emir Idris al-Sanusi to Egypt on 21 December 1922 deeply weakened the Libyan resistance. Before his departure, however, he appointed his brother Al-Rida as deputy and Umar al-Mukhtar as commander of the National Forces in the Green Mountains. This appointment placed military leadership in the hands of a figure able to maintain organized resistance after the movement’s central political authority had been disrupted.

Umar al-Mukhtar developed an effective form of mobile guerrilla warfare. He divided his forces into three major mobile companies, known as adwar, and established a camp in the mountainous area south of al-Mardj at Jardas. Italian attacks against his position in the summer of 1923 were repelled, as was another army sent against the camp in March. His forces relied on skirmishes, raids, ambushes, surprise attacks, and incursions across Cyrenaica.

Italy responded with measures intended to isolate the resistance from both external aid and local support. A wire fence was erected along the Tripoli-Egyptian border, oases were occupied, and rural inhabitants were transferred to fenced camps in the desert of Sirt. Umar al-Mukhtar nevertheless continued fighting and rejected an Italian offer of bribery during negotiations near al-Mardj on 19 July 1929. He was captured in September 1931, taken to Benghazi, and executed before thousands of Libyans at Suluk on 16 September.