Dear Leader. By Jang Jin-sung. Random House; 326 pages; $27.99. Buy from Amazon.com, Amazon.co.uk

WHEN Jang Jin-sung fled North Korea across the frozen Tumen river into China in 2004, he carried with him a small bundle of poems. These harrowing vignettes of North Korean hunger and suffering were later published in South Korea under a pseudonym.

Mr Jang had once composed paeans to Kim Jong Il, North Korea’s former ruler. In a new memoir, Mr Jang retraces his conversion from patriotic court poet to the Kim regime to one of its fiercest critics; from a privileged life within Pyongyang’s elite as one of Kim’s “Admitted” to being a destitute fugitive, on the run from North Korean agents in China, where he sought asylum in the South Korean embassy in Beijing. If his personal poems laid bare how the Kims gained power through cruelty and repression, Mr Jang’s latest account exposes the reach of their cultural dictatorship, which put literature and history at the service of an extraordinary and lasting personality cult.

Mr Jang was employed in North Korea as a poet in the United Front Department, an important party unit involved in organising psychological warfare against Koreans of all stripes. This made him familiar with its propaganda machinery. In the 1980s its literary output was directed at South Korean democracy movements, then resisting their own military dictator, in the hope of kindling pro-North sympathies in the South. By the 1990s the unit had turned inward, but still used many of the same South Korean tropes and idioms. Its authors pretended to be Southerners praising Kim Jong Il. To help him prepare, Mr Jang was given access to prohibited South Korean newspapers, television and books.

A paper shortage after the economy collapsed in the early 1990s led novels, a form that had been popular under Kim’s father, Kim Il Sung, to be replaced by epic poems. One of these, “Spring Rests on the Gun Barrel of the Lord”, composed in 1999, earned Mr Jang a rare meeting with Kim. He was admitted to an inner circle of six court poets and given immunity from prosecution.

North Korea’s leading propaganda poets were rewarded with imported cars and large flats. Officials, desperate to prove their loyalty to the Kim cult, vied for honours. But a chance encounter with Byron’s poetry (among works that were limited to a secret print run of 100 copies in North Korea) proved a delicious deviation from the strictures of Kim’s “Juche Art Theory”, a set of linguistic expressions to which all North Korean works must adhere.

As a state historian, Mr Jang was allowed to read banned portions of the country’s unvarnished history, the better to distort it. The more he read, the more he recognised how Kim had wrested power from his father. The swelling of the Kim Il Sung cult, which his son set in motion, legitimised Kim’s rule while justifying a shift of power away from his father. Under the pretext of lightening the Supreme Leader’s load, all proposals were routed through the party’s revamped Organisation and Guidance Department (OGD), headed by Kim. Eventually, only those that were deemed important were passed up to his father. Kim transferred the power to appoint and dismiss personnel to the OGD. Political enemies were watched and then purged.

Kim’s hereditary succession was not guaranteed at the start. Mr Jang offers considerable detail about how he set out to usurp his father, revealing the factional infighting and what he calls the “subterfuge and machinations” that pitted son against father; even Kim Il Sung’s own bodyguards came under OGD control. The dual structure of the Kim Il Sung cult, with the young Kim the real power behind the throne, allowed the son to confound outsiders. Foreigners scrutinised the seven pallbearers at Kim Jong Il’s funeral in 2011, but none held real power, Mr Jang says.

“Dear Leader”, which includes three personal poems, is a testament to Mr Jang’s literary flair. He chooses poetry to express painful episodes, whether the hunger of a young girl or the public execution of a farmer in his home town. He paints a bleak portrait of his village, to which he briefly returns to discover a swarm of wasted bodies “waiting for death”, a childhood friend eating rice by the grain and tap water for sale. Desolation creeps even into better-off Pyongyang: a mother, close to death, and her daughter stand in a marketplace; a sign hangs from the girl’s neck: “I sell my daughter for 100 won ($0.11)”.

The contrast with China’s bright cities, to which Mr Jang first escapes, could not be starker. He marvels at the “boldness of mankind in defying nature’s darkness”; at advertising hoardings more impressive than the Kim iconography. Yet, there too, he is hounded by North Korean and Chinese officials. He meets North Korean women who have fled both their country and their Chinese captors. Theirs are chilling tales of human trafficking. Graded and priced like pigs, many spend their lives “rotting”, shackled at night so they cannot escape. They also show great courage.

Mr Jang makes no claim to speak from within Kim Jong Il’s closest circle. But as a poet laureate, on the inside of the Kims’ mythmaking machine, he sheds new light both on the dynasty’s ideological underpinnings and on what he calls “the tantrums of a defeated man”.