[1] In order to create the shortest possible route from Japan to eastern Manchuria, the Chosen Government Railway (Sentetsu) began construction of a line from Unggi (now Sŏnbong) to Donggwanjin via Namyang in 1929.

This new route, using the northern port of Unggi, made the distance from Japan to Harbin even shorter than via Cheongjin.

[5] In addition to the connections to the Manchukuo National Railway at Sangsambong and Namyang, Mantetsu had a third connection to Manchukuo, via the privately owned East Manchuria Railway's bridge across the Tumen River at Hunyung.

[6] Service on the line was suspended after the Soviet invasion at the end of the Pacific War.

The damage sustained by the line during the war - including the destruction of the Tumen River bridges at both Hunyung and Sambong - was slow to be repaired due to strained relations between the Soviets and the Korean People's Committees; those two bridges have not been repaired to the present day.