Historians contend that for the UN and North Korea, locked in a bitter battle where neither could gain the upper hand, logistics was among the most important determining factors in how the war would progress. As the disparity in logistics capability widened between the UN and North Korean forces, the well-supported UN troops were able to hold their positions along the Pusan Perimeter, while the morale and the fighting quality of NKPA deteriorated as resupplies became increasingly unreliable. This trend ultimately culminated in the UN recapturing Seoul, the key logistics center of the battle, and the collapse of the North Korean logistics system with the entire NKPA.