Catholicism came first, from 1785. The early converts were harshly persecuted - so much so that when in the 1980s these martyrs were canonized en masse, Korea instantly acquired the world's fourth largest quota of saints. Protestants arrived a century later, playing a pioneer role in education and health from the 1880s which continued under Japanese occupation. Many fled south. By the 1950s all churches and temples were closed, and would remain so for three decades.
Critics claim Pyongyang's trio of churches is purely cosmetic and mainly for external consumption.
Yet a service I attended in 1990 felt genuine, if constrained. The worshippers seemed to be not so much actors, as believers who had proved their loyalty to the regime - much as, by the 1940s, Korean Christians had to acknowledge the divinity of the Japanese emperor if they wanted to stay in business. But there are others. The iconography of the Kim cult clearly borrows from Christianity. In another apparent move to be more inclusive, a few years ago North Korea claimed to have found the grave of Tangun, the mythical founder of Korea and an object of worship for some in South Korea.