James Dennis, 1986
Unless you have been assigned to Korea, you probably have never heard of a Hardened Artillery Site (HARTS). This is partially due to the US Army’s concentration on European-style maneuver warfare and partially because the HARTS are a North Korean peculiarity, developed in reaction to their experiences during the Korean Conflict, which was fought much like World War I. During that time, the UN Command gave the Chinese and North Koreans a graduate course on what 105mm, 155mm and 203mm artillery and Close Air Support (CAS) could do to a bunker system or trench line. From this, the North learned what measures were needed to protect their forces and have used this knowledge and the intervening time to prepare.
https://nautilus.org/publications/books/dprkbb/military/dprk-briefing-book-harts-in-north-korea/
