The strong measures taken against the nationalists by the Allies in March 1920 began a distinct new phase of the conflict. Mustafa Kemal sent a note to the governors and force commanders, asking them to conduct elections to provide delegates for a new parliament to represent the Ottoman (Turkish) people, which would convene in Ankara. Mustafa Kemal appealed to the Islamic world, asking for help to make sure that everyone knew he was still fighting in the name of the sultan who was also the caliph. He stated he wanted to free the caliph from the Allies. Plans were made to organise a new government and parliament in Ankara, and then ask the sultan to accept its authority.

A flood of supporters moved to Ankara just ahead of the Allied dragnets. Included among them were Halide Edip and Abdülhak Adnan (Adıvar), Mustafa İsmet Pasha (İnönü), Mustafa Fevzi Pasha (Çakmak), many of Kemal's allies in the Ministry of War, and Celalettin Arif, the president of the now shuttered Chamber of Deputies. Celaleddin Arif's desertion of the capital was of great significance, as he declared that the Ottoman Parliament had been dissolved illegally.

Some 100 members of the Ottoman Parliament were able to escape the Allied roundup and joined 190 deputies elected around the country by the national resistance group. In March 1920, Turkish revolutionaries announced the establishment of a new parliament in Ankara known as the Grand National Assembly (GNA). The GNA assumed full governmental powers. On 23 April, the new Assembly gathered for the first time, making Mustafa Kemal its first Speaker and Prime Minister and İsmet Pasha, Chief of the General Staff.

Hoping to undermine the national movement, Mehmed VI passed a fatwa to qualify the Turkish revolutionaries as infidels, calling for the death of its leaders. The fatwa stated that true believers should not go along with the nationalist (rebels) movement. The mufti of Ankara Rifat Börekçi issued a simultaneous fatwa, declaring that the Constantinople was under the control of the Entente and the Ferid Pasha government. In this text, the nationalist movement's goal was stated as freeing the sultanate and the caliphate from its enemies. In reaction to the desertion of several prominent figures to the Nationalist Movement, Ferid Pasha ordered Halide Edip, Ali Fuat and Mustafa Kemal to be sentenced to death in absentia for treason.