When the North Korean People’s Army made a dramatic breakthrough early in the war, T. R. Fehrenbach explains (in This Kind of War), it revealed what was to be a continuing weakness of the Communist armies in Asia:
They could break through the U.N. lines, but they could not exploit their local successes. With poor communications and even poorer systems of supply, dependent solely upon manpower to move their resupply, the enemy could not move quickly enough to exploit, particularly in the teeth of superior airpower, armor, and artillery. To put it simply, faced with breakthrough, the U.N. forces could retreat, and counterattack faster than the Inmun Gun could press their advantage. Whenever the heavier-armed United States Army could form continuous battle lines and withhold a reserve, the Communist tactics were doomed to failure.
If the NKPA had had a mechanized force capable of moving on Miryang, and an air force able to keep the Fifth Air Force off their backs, their tough and aggressive infantry might easily have split the beachhead and precipitated a U.N. disaster.