n late 2013, Jang Song-thaek, an uncle of Kim Jong-un, the North Korean leader, was taken to the Gang Gun Military Academy in a Pyongyang suburb. Hundreds of officials were gathered there to witness the execution of Mr. Jang’s two trusted deputies in the administrative department of the ruling Workers’ Party. The two men, Ri Ryong-ha and Jang Su-gil, were torn apart by antiaircraft machine guns, according to South Korea’s National Intelligence Service. The executioners then incinerated their bodies with flamethrowers. SNIP In his memoir, a Japanese sushi chef for Kim Jong-il from 1988 to 2001 who goes by the...