In the opening hours of the next Korean War, the North could kill upwards of 250,000 people using just conventional artillery, to say nothing of nuclear weapons or ballistic missiles, a January 2019 Rand Corporation report found. Those numbers are just from the South Korean capital alone.

And there is little the United States could do about it.

The North’s big gun is essentially a self-propelled coastal defense gun, the Koksan 170 mm, mounted on a tank and firing rocket-propelled shells up to 40 miles in any direction. Since the crews work outside of the weapon and North Korea’s air force could do little to protect them, the North had to devise a means of reloading the guns after firing, when they’re exposed and vulnerable.

Some 10 million people live within firing range of the Korean demilitarized zone, living and working every day with hundreds of guns pointed at their heads. This includes the population of Seoul as well as the tens of thousands of U.S. and South Korean military personnel stationed on the peninsula. Most of them live within the 25-mile range of Communist artillery pointed at the South; but North Korea has some pieces that can fire as far as 125 miles, affecting a further 22 million people. It’s not a good situation for defending South Korea or protecting our forces.

“Conservative predictions of a likely attack scenario anticipate an initial artillery barrage focused on military targets, which would result in significant casualties,” said U.S. Army Gen. Vincent Brooks, head of U.S. Forces Korea. “A larger attack targeting civilians would yield several thousand casualties with the potential to affect millions… within the first 24 hours.”

North Korea has thousands of artillery pieces that could fire tens of thousands of rounds during a 10-minute barrage. The big Koksan 170 carries 12 rounds of its own before it has to go re-arm itself. Since any ammunition depots would be as vulnerable to enemy aircraft as the artillery themselves, North Korea has constructed thousands of reinforced underground bunkers near the DMZ to hold ammo and house the guns.

As a result, in an opening salvo, North Korean artillery is likely to use what military planners call a “shoot n’ scoot” tactic. The guns will come out of the bunkers to fire off their rounds and then go right back into hiding to reload and prepare for another volley in rapid succession. This will make it difficult for allied airpower to track and kill the weapons.

The best scenario for Seoul is that the Koksan 170 requires a specialized round to hit Seoul, one the North may have in limited quantities. Even if they do fire at a high rate, it’s likely the barrels of the weapons will heat up to a degree that the ideal rate of fire U.S. military planners plan against won’t be the actual rate used in combat.

Another potential advantage for the UN forces is the area covered by the guns. If North Korea wants to destroy Seoul in the first few minutes of a war, all of its weapons would need to be trained on Seoul, work perfectly, and have the maximum rate of fire for a skilled crew – while UN planes and artillery are shooting back.

Unlikely.