Richard L. Kugler

North and South Korea Military Balance, by the Numbers

Richard L. Kugler, PhD/

Why North Korea’s Military Force Currently Could Not Conquer South Korea

Some analysts fear that if the North Korean army invaded South Korea, the North could quickly defeat South Korea’s army and overrun the entire country. In my judgment, the South Korean army backed by U.S. air power is plenty strong enough to rebuff a North Korean attack. Inevitably a war on the Korean peninsula would be highly violent and uncertain, but the odds are high that a North Korean attack would be stopped near the Demilitarized Zone (DMZ), and immense losses would be inflicted on enemy forces.

Data on the military situation in Korea is available in IISS’s Military Balance 2017. On paper, the North Korean army seems superior to the south. North Korea fields an army of a million troops that includes 46 divisions, 4000 tanks, and 8500 artillery tubes for firing conventional munitions. By contrast, South Korea fields a smaller army of 500,000 troops that includes 30 divisions, 2400 tanks, and 5000 artillery tubes. But when an army is defending from prepared positions on mountainous terrain, it does not need to be as large as its opponent. This especially holds true in Korea, whose many steep mountains north of Seoul make an enemy attack difficult. What matters is whether South Korea has enough ground forces to form a strong defense line along the 160-mile DMZ and to mobilize sufficient reserves to block North Korean forces from advancing down the few, small attack corridors along the DMZ. The South Korean army is easily large enough and properly equipped to perform this mission, and it has had over 60 years to prepare the terrain north of Seoul with an extensive network of fortifications, infantry trenches, tank barriers, and roadblocks that would impede a North Korean assault.

An additional, important factor in the military equation is the air balance, which strongly favors South Korea and the United States. North Korea has a weak air force of 500 mostly obsolescent fighters inherited from the Cold War. By contrast, South Korea has 500 mostly modern fighters that include 200 F-15 and F-16s. Within a few days, the United States could provide about 350 modern fighters as reinforcements: all of them would be highly lethal against North Korean air and ground forces. Together, South Korean and U.S. air forces could quickly seize control of the air, devastate North Korean ground forces caught in the open, and bomb such North Korean targets as its artillery sites and Pyongyang.

The principal risk is that the North Korean military, if unleashed by the country’s unpredictable and pathological dictator, could employ its long-range artillery to bombard Seoul and inflict major destruction on it. But the odds that North Korean ground forces could conquer Seoul and advance deeply into South Korea are low. The greater likelihood is that they would be stopped in their tracks and destroyed by South Korean and U.S. forces, which would be able to counterattack into North Korea in the aftermath. This situation could change if and when North Korea acquires a sizable arsenal of deliverable nuclear warheads in the years ahead. If this occurs, the United States will be compelled to use its own nuclear weapons to extend a firm umbrella of deterrence coverage over South Korea. Until then, the current military balance in Korea is relatively stable, and war is unlikely to occur provided South Korea remains militarily strong and the United States continues using its power to enforce containment and deterrence on the Korean peninsula.

In summary, the military balance in Korea is undeniably something to worry about, but in ways that keep matters in perspective. Yes, North Korea today poses a major offensive threat to South Korea. But a North Korean ground and air attack across the DMZ would encounter a strong South Korean army, many mountains, extensive terrain fortifications and tank barriers, and formidable U.S. and South Korean air strikes. Likely, the North Korean military would come away battered and destroyed, not victorious. This is a core reason why, despite many alarming political crises, war has not broken out on the Korean peninsula since 1953, and is unlikely to occur today.