When it was necessary, mortars would fire flares over no-man’s land. These produced an eerie but effective light before slowly floating back to earth by small parachute. Another thing we got used to was the sound of a high flying slow aircraft that flew over the front line emitting an enormous flash, presumably to photograph the enemy’s night time movements.
The UN had total control of the air, except for the very rare single craft which quickly retreated again. This meant that all the enemy’s supplies and manpower was done in the dark for fear of air attack. The subdued headlights of trucks could be seen as they passed between hills. The UN could resupply at any time. However, the contours of the country, namely dirt track roads winding through valleys surrounded by steep hills suited the Chinese/North Korean mostly non mechanised and foot-slogging soldiers especially when in close combat.
In the early days of the war, and well before my time, it was not difficult to trap a group of retreating UN tanks, or other vehicles, by blowing up the lead vehicle then descend from the adjoining hills to massacre our men. The terrain was mostly of a nature that vehicles diverting off the basic road would soon get bogged down either in the paddy fields or roadside ditches.