The Fifth Campaign -- Part 2 During this period, our forces had constructed a network of good fortifications. The surface defensive positions of our forces were giving way to fortifications built under ground. A defense-in-depth tunnel system was taking place gradually along the 38th Parallel. (A total of 1,250 km. of tunnels and 6,240 km. of trenches involving the shifting of 60 million cubic meters of rock and earth were dug along the front by the Chinese People's Volunteers and the Korean People's Army during the war.) The tunnel fortifications were so strong that no enemy troops could penetrate them (an example was provided by the tunnel fortifications of the Sangkumryung Ridge). As a result, the enemy attacks were repulsed one after another. In 43 days of fighting ending November 25, 1952, the U.S, forces dumped 10,000 bombs and 1,900,000 shells that blasted away two meters of rock from the summits of a small cluster of heights known as Sangkumryung Ridge. Fighting back from the tunnel fortifications built deep underground, the Chinese People's Volunteers repulsed no fewer than 900 attacks on the hills, inflicting a total of 25,000 casualties on the enemy.

With the emergence of strongly built defenses in the summer and autumn of 1951, our forces began to employ Chairman Mao's "piece-meal" attack method against the enemy. In launching an attack, our troops concentrated camouflaged offensive positions to bring maximum firepower to bear on the enemy -- usually a battalion -- was wiped out. We fought many such battles -- around four or five a month. The numbers of enemy troops put out of action were not small when they were added up.

Moreover our forces had mastered the tactic of storming strongly fortified defenses in positional warfare. The last battle in which our forces stormed enemy defenses took place one evening in late July 1953, when four of our armies cut through a 25 X 25 kilometer gap in the enemy's bunker defense system in a single night just before the Armistice Agreement. Our forces wiped out a heavy artillery regiment of the U.S. Army and a great part of four puppet divisions.