[9] Differences emerged between North Korea and the Soviet Union; chief among them was Kim Il Sung's philosophy of Juche, which focused on Korean nationalism and self-reliance.

During this period, North Korea also remained critical of the United States defense force's presence in the region, which it considered imperialist, having seized the American ship USS Pueblo in 1968.

He then attended Yuwen Middle School in China's Jilin province until 1930,[21] when he rejected the feudal traditions of older-generation Koreans and became interested in communist ideologies.

[31] Even more significant than the military success itself was the political coordination and organization between the guerrillas and the Korean Fatherland Restoration Association, an anti-Japanese united front group based in Manchuria.

However, Soviet military officer Yakov Novichenko grabbed the grenade and absorbed the blast with his body, leaving Kim and other bystanders unharmed.

[43][44][45] To solidify his control, Kim established the Korean People's Army (KPA), aligned with the Communist Party, and he recruited a cadre of guerrillas and former soldiers who had gained combat experience in battles against the Japanese and later against Nationalist Chinese troops.

Prior to Kim's invasion of the South in 1950, which triggered the Korean War, Stalin equipped the KPA with modern, Soviet-built medium tanks, trucks, artillery, and small arms.

[49] In 2019, investigative journalist Annie Jacobsen published the book Surprise, Kill, Vanish, which further expounded that the U.S. Central Intelligence Agency (CIA) once concluded that Kim Il Sung was a blackmailed imposter operated by the Soviet Union.

Jacobsen also writes that the CIA learned "specific instructions [were] given to the leaders of the regime that there should be no questions raised about Kim [Il Sung]'s identity.

Evidence suggests that Soviet intelligence, through its espionage sources in the US government and British SIS, had obtained information on the limitations of US atomic bomb stockpiles as well as defense program cuts, leading Stalin to conclude that the Truman administration would not intervene in Korea.

[58][59][60] The Chinese did not provide North Korea with direct military support (other than logistics channels) until United Nations troops, largely US forces, had nearly reached the Yalu River late in 1950.

But in September, the North Koreans were driven back by the US-led counterattack that started with the UN landing in Incheon, followed by a combined South Korean-US-UN offensive from the Pusan Perimeter.

[62][63] On 25 October 1950, after sending various warnings of their intent to intervene if UN forces did not halt their advance,[64]: 23  Chinese troops in the thousands crossed the Yalu River and entered the war as allies of the KPA.

[65] Chinese and Russian documents from that time reveal that Kim became increasingly desperate to establish a truce, since the likelihood that further fighting would successfully unify Korea under his rule became more remote with the UN and US presence.

[73][74] Kim developed the policy and ideology of Juche in opposition to the idea of North Korea as a satellite state of China or the Soviet Union.

The North Korean ambassador to the USSR, Li Sangjo, a member of the Yan'an faction, reported that it had become a criminal offense to so much as write on Kim's picture in a newspaper and that he had been elevated to the status of Marx, Lenin, Mao, and Stalin in the communist pantheon.

He also charged Kim with rewriting history so it would appear as if his guerrilla faction had single-handedly liberated Korea from the Japanese, completely ignoring the assistance of the Chinese People's Volunteers.

Li reported that over 30,000 people were in prison for completely unjust and arbitrary reasons which were as trivial as not printing Kim Il Sung's portrait on sufficient quality paper or using newspapers with his picture to wrap parcels.

Each person was classified as belonging to the "core", "wavering", or "hostile" class, based on his or her political, social, and economic background—this caste system persists today.

Large numbers of people from the so-called hostile class, which included intellectuals, land owners, and former supporters of Japan's occupying government during World War II, were forcibly relocated to the country's isolated and impoverished northern provinces.

Not only dissenters but their entire extended families were punished by being reduced to the lowest songbun rank, and many of them were also incarcerated in a secret system of political prison camps.

[85] At the same time, Kim reinstated relations with most of Eastern Europe's communist countries, primarily with Erich Honecker's East Germany and Nicolae Ceaușescu's Romania.

[86] In the 1960s, Kim became impressed with the efforts of North Vietnamese Leader Ho Chi Minh to reunify Vietnam through guerrilla warfare and thought that something similar might be possible in Korea.

[87]: 33 Albania's Enver Hoxha (another independent-minded communist leader) was a fierce enemy of the country and Kim Il Sung, writing in June 1977 that "genuine Marxist-Leninists" will understand that the "ideology which is guiding the Korean Workers' Party and the Communist Party of China ... is revisionist" and later that month he added that "in Pyongyang, I believe that even Tito will be astonished at the proportions of the cult of his host [Kim Il sung], which has reached a level unheard of anywhere else, either in past or present times, let alone in a country which calls itself socialist.

It has been argued, however, that the incident helped establish the order of succession – the first apparent patrilineal in a communist state – which eventually would occur upon Kim Il Sung's death in 1994.

[97]: xii To ensure a full succession of leadership to his son and designated successor Kim Jong Il, Kim turned over his chairmanship of North Korea's National Defense Commission – the body mainly responsible for control of the armed forces as well as the supreme commandership of the country's now million-man strong military force, the Korean People's Army – to his son in 1991 and 1993.

[98] To the astonishment of the United States and the International Atomic Energy Agency, Kim agreed to halt his nuclear research program and seemed to be embarking upon a new opening to the West.

[110][116] Kim Il Sung was revered as a godlike figure within North Korea during his lifetime, but his personality cult struggled to extend beyond the country's borders.

[120] Kim Il Sung's image is prominent in places associated with public transportation, especially his posthumous portrait released in 1994, which hangs at every North Korean train station and airport.

[121] At the border outside of Yanji, South Korean tourists could pay the local Chinese residents for a picture taken against the scenery of North Korea beyond the Tumen River, with the portrait of Kim Il Sung looming large at the background.