Purge of the "Domestic faction"
As the Korean War drew to a close, he first moved against the Domestic faction. While the Soviet faction had the sponsorship of the Soviet Union and the Yanan faction was backed by China the Domestic faction had no external sponsor who would come to their aid and was therefore in the weakest position. With the end of the Korean War the usefulness of the Domestic faction in running guerilla and spy networks in South Korea came to an end. Former leaders of the Workers Party of South Korea were attacked at a December 1952 Central Committee meeting. In early 1953 rumours were spread that the "southerners" had been planning a coup. This led to the arrest and removal from power of Pak Hon-yong (who was foreign minister at the time) and Yi Sung Yopo the minister of "state control" who was charged with "spying on behalf of the United States".
In August 1953, following the signing of the armistice that suspended the Korean War, Yi and eleven other leaders of the domestic faction were subjected to a show trial on charges of planning a military coup and sentenced to death. In 1955, Pak Hon Yong, the former leader of the WPSK and deputy chairman of the WPK, was put on trial on charges of having been a US agent since 1939, sabotage, assassination, and planning a coup. He was sentenced to death, although it is unclear if he was shot immediately or if his execution occurred some time in 1956.
The trials of Yi and Pak were accompanied by the arrest of other members and activists of the former SWPK with defendants being executed or sent to forced labour in the countryside. The domestic faction was virtually wiped out, though a few individual members who had personally allied themselves to Kim Il-sung remained in positions of influence for several more years.
The "August Incident" and aftermath
Kim Il-sung sent out preliminary signals in late 1955 and early 1956 that he was preparing to move against the Yanan and Soviet factions. The Twentieth Party Congress of the Soviet Communist Party was a bombshell with Nikita Khrushchev's Secret Speech denouncing Stalin and the inauguration of destalinisation. Throughout the Soviet bloc domestic Communist parties inaugurated campaigns against personality cults and the general secretaries who modelled themselves after Stalin were deposed throughout Eastern Europe.
Kim Il-sung was summoned to Moscow for six weeks in the summer of 1956 in order to receive a dressing down from Khrushchev, who wished to bring North Korea in line with the new orthodoxy. During Kim Il-sung's absence Pak Chang Ok (the new leader of the Soviet faction after the suicide of Ho Ka Ai), Choe Chang Ik, and other leading members of the Yanan faction devised a plan to attack Kim Il-sung at the next plenum of the Central Committee and criticise him for not "correcting" his leadership methods, developing a personality cult, distorting the "Leninist principle of collective leadership" his "distortions of socialist legality" (i.e. using arbitrary arrest and executions) and use other Khrushchev-era criticisms of Stalinism against Kim Il-sung's leadership.
Kim Il-sung became aware of the plan upon his return from Moscow and responded by delaying the plenum by almost a month and using the additional time to prepare by bribing and coercing Central Committee members and planning a stage-managed response. When the plenum finally opened on August 30 Choe Chang-ik made a speech attacking Kim Il-sung for concentrating the power of the party and the state in his own hands as well as criticising the party line on industrialisation which ignored widespread starvation among the North Korean people. Yun Kong Hum attacked Kim Il-sung for creating a "police regime". Kim Il-sung's supporters heckled and berated the speakers rendering them almost inaudible and destroying their ability to persuade members. Kim Il-sung's supporters accused the opposition of being "anti-Party" and moved to expel Yun from the party. Kim Il-sung, in response, neutralised the attack on him by promising to inaugurate changes and moderate the regime, promises which were never kept. The majority in the committee voted to support Kim Il-sung and also voted in favour of repressing the opposition expelling Choe and Pak from the Central Committee.
Several leaders of the Yunan faction fled to China to escape the purges that followed the August plenum while supporters of the Soviet faction and Yanan faction were rounded up. Though Kim Tu Bong, the leader of the Yanan faction and nominal President of North Korea was not directly involved in the attempt on Kim he was ultimately purged in 1958 accused of being the "mastermind" of the plot. Kim Tu Bong "disappeared" after his removal from power and likely was either executed or died in prison.
In September 1956 a joint Soviet-Chinese delegation went to Pyongyang to "instruct" Kim Il-sung to cease any purge and reinstate the leaders of the Yanan and Soviet factions. A second plenum of the Central Committee, held on September 23, 1956, officially pardoned the leaders of the August opposition attempt and rehabilitated them but in 1957 the purges resumed and by 1958 the Yanan faction had ceased to exist. Members of the Soviet faction, meanwhile, facing increased harassment, decided to return to the Soviet Union in increasing numbers. By 1961 the only faction left was Kim Il-sung's own guerrilla faction along with members who had joined the WPK under Kim Il-sung's leadership and were loyal to him. In the 1961 Central Committee there were only two members of the Soviet faction, three members of the Yanan faction and three members of the Domestic faction left out of a total Central Committee membership of 68. These individuals were personally loyal to Kim Il-sung and were trusted by him; however, by the late 1960s, even these individuals were almost all purged.
One likely reason for the failure of the Soviet and Yanan factions to depose Kim Il-sung was the nationalist view by younger members of the party who had joined since 1950 that the members of these factions were "foreigners" influenced by alien powers while Kim Il-sung was seen as a true Korean.