In February 1947, his forces escorted Kartosoewirjo to Malang to attend the plenary session of Central Indonesian National Committee.
[1][2] In mid-August 1948, Suhario, with his three Hisbullah companies, moved to the Brebes-Tegal area to wage a guerilla war against the Dutch.
[3][1] In September 1948, Fatah tried to meet Kartosoewirjo in West Java to convince him not to proclaim an islamic state and to remain loyal to Indonesia.
From a meeting with Kamran, Fatah changed his mind from opposing Kartosoewirjo's Islamic state conception to supporting it.
[6] On 19 December 1948, the Dutch launched Operation Kraai and TNI units, which were forced to move to the Republican control area due to the Renville Agreement, retreated to their respective origin to wage guerrilla against Dutch and formed military government.
He felt threatened by the presence of the TNI military government in the Brebes-Tegal area because it had close relations with the left-wing group.
[8] Hence, on 28 April 1949, Amir Fatah proclaimed the establishment of the Islamic State of Indonesia in Pengarasan, Brebes.
Eventually, Amir Fatah and his forces surrendered to TNI in Calingcing, Tasikmalaya, on 20 December 1950.
[2] Fatah was imprisoned in Nusa Kambangan and later transferred to unknown prison in West Java.