From: Los Angeles
But I think they count much of their population in that figure and their supply situation isn't exactly up to snuff.
That's a key consideration, all right. Any prolonged war would collapse the North Korean economy, which is already on life support courtesy of China. At a wild guess, Pyongyang would have perhaps two weeks to force a South Korean surrender. After that, their troops would run out of food, fuel, and firepower. And this time it is unlikely that the Russians and Chinese would resupply them.
Concerning artillery: first point is that modern artillery would need only a few hours to reduce a city to non-functional status. If the North Koreans used phosphorus or other incendiaries, the secondary effects could be severe. Second point is that U.S. counter-battery fire would, IMHO, not be terribly effective. Artillery has been a weak point of the U.S. Army for some time. (During Desert Storm we discovered that the Iraqis had better guns than we did.) More, there are fewer than 30,000 U.S. troops left in Korea at the moment. The Pentagon has for a long time relied on airstrikes rather than cannons for long-range damage.
And this is why the Prime Minister of Japan just lost his job. He had pledged to remove the U.S. base from Okinawa entirely. But, if a quick glance at the map is correct, that is the closest significant base to Korea (other than those in Korea itself). The American government informed him that they would consider re-locating the base to another point on the island, but moving off the island entirely was a non-starter.
Civil war? What does that mean? Is there any foreign war? Isn't every war fought between men, between brothers?