With North Korea making the world's headlines on a fairly regular basis, in researching the nation, I stumbled on an interesting bit of recent history - OPPLAN 5027, the United States - Republic of Korea Combined Forces Command warplane.
The original OPPLAN 5027, was designed to oppose a North Korean invasion. A 50 mile retreat from the demilitarized zone (DMZ) would bring allied forces to the Hollingsworth line south of the Han River where it bisects the capital of South Korea. Troops would wait here until they were reinforced and then push forward, pushing North Korean forces back to the north.
In 1973 - 1974, United States General James Hollingsworth developed a new version of OPPLAN 5027, known as OPPLAN 5027 -74, that would see the movement of allied tanks, infantry and artillery toward the Military Control Zone (MCZ) located five miles south of the DMZ as shown on this map:
It was hoped that this tactic would convince the North Koreans that an invasion was futile since a rapid deployment of both ground troops and bomber sorties into DPRK territory was likely and that capturing the capital city, Pyongyang, was quite possible. General Hollingsworth predicted that this lightning invasion would defeat North Korea in a few days with his nine day war plan. At the time, the Congressional Budget Office predicted that, without the use of nuclear weapons, if the North looked set to defeat the allied forces, Seoul could fall into North Korean hands.
Throughout the period from 1991 to 1994, the United States had repeatedly tried to coerce and force North Korea into halting its nuclear program which, at the time, saw North Korea removing spent fuel rods containing plutonium from its nuclear reactor at Yongbyon and the country's withdrawal from the Nuclear Nonproliferation Treaty. On June 16th, 1994, after not being able to determine whether the DPRK had sufficient plutonium to create one or two nuclear weapons, President Bill Clinton dispatched military reinforcements to South Korea.
OPPLAN 5027 under went further fine-tuning in 1994 and in this scenario, South Korean forces were able to reach a stalemate with DPRK forces at a point 20 to 30 miles south of the DMZ. At that point, a combination of U.S. and ROK forces would state a major air campaign against northern forces. A division of Marines along with divisions of ROK forces would launch an overland offensive from the east coast of North Korea followed by an advance on the west coast toward Pyongyang accompanied by a major counteroffensive from a staging area north of Seoul. This plan included counteroffensive measures that would have seen the toppling of the North Korean's Eternal President, Kim Il Sung).
OPPLAN 5027 was further overhauled throughout the 1990s, ensuring the availability of Japanese bases should American forces need them in the event of an invasion of North Korea. OPPLAN 5027 -98, adopted in 1998, focussed on offensive operations into the DPRK with the goal of "abolishing North Korea as a functioning state, ending the rule of its leader Kim Jong Il and reorganizing the country under South Korean control.". The plan also concentrated on North Korea's chemical and biological weapons capabilities which, it was estimated, could kill up to 38 percent of Seoul's 12 million residents. In 1992, South Korea released information that North Korea had 1000 tonnes of chemical weapons held in six storage facilities, a 400 percent increase over five years earlier. More recent reports from South Korea estimates the size of the DPRK's stockpile of chemical weapons at between 2500 and 5000 tonnes, among these, blistering agents, nerve agents, choking agents, blood agents and tear gas. OPPLAN 5027-98 included pre-emptive strikes against North Korean military bases throughout the country if intelligence detected that the North was preparing to strike at South Korea.
In OPPLAN 5027-00, the plan upped the ante. In the early 1990s, the U.S. planned to deploy 480,000 troops in the event of hostilities. By the year 2000, this number had risen to a whopping 690,000 troops from the Army, Air Force, Navy and Marine Corps, 160 Navy ships and 1600 aircraft, all deployed from the United States within a 90 day period. Carrier battle groups with advanced fighters, tactical fighter wings and marine expeditionary forces from both Okinawa and the U.S. mainland would be dispatched to the Korean theatre.
By 2004, OPPLAN 5027-04 had been altered to allow the United States to respond to North Korean hostilities without waiting for as many ground troops to arrive by using air power rather than artillery and by using missile defense systems including anti-missile interceptors.
A war on the Korean peninsula would be devastating. Seoul, with a population of 10.4 million people, contains one quarter of South Korea's entire population and is located about 30 miles south of the DMZ. North Korea, while it may appear culturally and economically backward, has a substantial military with between 1 million and 1.2 million citizens in its Korean People's Army, ranked number four in the world by size. It also has an estimated 8.2 million reserve personnel putting the nation at number one by size. Ground forces have access to 3800 tanks, 2270 APCs and 11200 pieces of artillery, most of which are self-propelled for rapid deployment. The Air Force has a total of 103000 personnel, operating 1670 aircraft, most of which are obsolete. If South Korean intelligence is right, North Korea has a collection of missiles capable of delivering a deadly cargo as shown here:
Here is a chart showing a comparison of troop and equipment strength for both North and South Korea:
As was the case in the 1950s version of the Korean War, China's close relationship with their North Korean counterparts is a complicating issue. China's intervention in North Korea changed the entire complexion of the first Korean war just as it is likely to change the outcome of the next. After all, the People's Republic of China maintains the world's largest military force based on manpower with an estimated 2.3 million troops in the People's Liberation Army. That, once again, is a game changer.