This is an article that looks into the idea of what if the North Koreans had invaded South Korea instead of launching a rocket into space. Anyone is free to add edits, but please try to follow the timeline
Start of the Second Korean War
On May 4th, 2012, it all started. North Korea fired three rockets, the Taepodong-1, armed with a ballistic warhead at Seoul, South Korea, at 5:30 PM, ET. The rockets impacted a 5:59 PM, ET in and around the Nowon District, killing approximately 284,921 civilians, and injuring over half a million. The United States South Korean Command fire a Patriot Missile, but it failed to impact due to little warning.
The United States had seen the rockets being prepared in previous weeks, but the North Korean government had claimed it was launching three satellites, still violating UN sanctions, and even giving flight routes for aircraft to avoid.
Ten minutes after impact, the South Korean armed forces were preparing to retaliate against the North Korean government by launching retaliatory airstrikes against missile sites and military bases. But the United States convinced the South Korean military to stand down, as the US ordered its forces to go to DEFCON Level 3. South Korea deployed the 3rd Armored Brigade to the DMZ, and the 21st, 22nd and 23rd Infantry Regiments, supported by the 103rd fighter squadron flying F-5 Tiger II.
That morning in New York City, the UN called an emergency meeting with all members. All nations in attendance condemned the assault, given the fact that it was an unprovoked assault and the high civilian casualty rate, except for Iran and Syria who praised Kim Jong Un for his "Bravery in standing up to the American Terrorists."
The same day, South Korea pulled out of Kaesong Industrial Complex after North Korea arrested several businessmen.
More sanctions were voted into effect including cut of all monetary aid foodstuff, and medical help. North Korea threatened to launch a nuclear strike into South Korea and Japan. South Korea, worried is reassured by the US that, although they will not return in kind, will support an invasion, and shoot down incoming missiles. The United States Government sent the USS Harry S. Truman aircraft carrier task force to the Yellow Sea and a small destroyer task force in the Sea of Japan. On May 27th, a North Korean Submarine torpedoed the USS Dewey, and sank it, killing all on board. The US ordered North Korea to apologize, which it refused, leading to an investigation by the UN Security Council.
The next day North Korea announced that it was reactivating several old deactivated nuclear facilities and stepping up its uranium enrichment programs. It was also revealed that they had around five or six Musudan missiles armed with crude plutonium warheads.
All US forces on the Pacific Rim were put on DEFCON 2, a level not used since the end of the Cold War. Anti-aircraft weapons were loaded, while fighter jets were fueled and missiles were readied. Ten thousand US infantry soldiers were moved to the DMZ, along with a tank battalion. Japan deployed six thousand troops into South Korea, and moved three cruisers to the Yellow Sea.
The War Starts
On May 17th, Kim Jong Un believes that the US and South Korea are weak. He orders the heavy guns to fire again until they destroy Seoul. At 6:14 AM, the guns open fire, pounding Seoul, hitting the US Embassy and civilian housing, killing another one-thousand civilians, and wounding another 17,000. After firing for fifteen minutes they all cease to allow the bombers and special operations units to enter undamaged. Then troops from the DMZ are sent in through the DMZ, backed by a tank division, a squadron of Beagle bombers, and two squadrons of MiG-21 fighter jets from the Koksan Airport. Immediately, the US South Korean Command and Japanese Command get word of this assault. They order all US troops to fire on sight at the enemy, and fighters to be scrambled as soon as they are fueled and prepped.
The South Korean Air Force scrambles the F-5's immediately and orders all other air units to prepare to launch at command. Meanwhile, the army deployed all available combat units up to the DMZ, and begin to ready the area for war.
In the United Nations, most nations called upon the nations involved to cease hostilities and move to their respective sides of the DMZ. The United States called for sanctions on North Korea and UN supported combat missions to the Korean Peninsula to prevent the fighting from escalating. North Korea's ambassador demands the US withdraws from Korea, and that Chinese troops replace them.
By the next day, South Korean freighters were being torpedoed by North Korean submarines and the South was losing most of the oil imports it needed to fight the war. Soon South Korean fighters began to bomb North Korean supply lines from China and Russia, occasionally firing over the North Korean border into these other countries. Meanwhile, Seoul and other major cities were being pounded by over 10,000 artillery and missile units, prompting mass evacuations south by the government and people.
The United States and South Korean Air Forces were easily holding off the North Korean Air Force, due to quality of aircraft and pilots. To cut down on artillery strikes, the US Army sends out Apache attack helicopters, supported by F-16's, F-22's, and B-52's to destroy as many as possible. The fighters neutralized air defense while the B-52's destroyed open air artillery batteries and the attack helicopters would eliminate bunker units.
The US and South Korean governments relocated the capitol to Busan. Meanwhile, South Korean infantry managed to push the North Korean advance to a halt and in some small pockets forced them back over the DMZ. Meanwhile, North Korean sleeper agents raided and damaged the Iljin Nuclear Power Plant, temporarily disabling it. South Korea declared martial law for the northern part of the country and began evacuating large portions of the population to Jeju and the southern provinces. Japan and Taiwan requested their citizens evacuate and return home, sending passenger liners to speed the process up. All nations evacuate nonessential personnel from embassies and consulates in both Koreas.
On May 22nd, the 16th Army of the PRC joined North Korean troops in fighting, inflicting heavy casualties on US and Japanese soldiers who fiercely resisted their advances. The United States mobilized soldiers that were in the Middle East and moved them to fight in the Second Korean War. Infantry and tanks were moved from Japan into South Korea and fighter jets harassed North Korean supply lines. Meanwhile, China launched an invasion into Taiwan, with the RoC barely holding off the invasion by air and sea.
In the United States, there were clashed similar to Vietnam between the 'doves' and the 'hawks'. In New York City, Mayor Bloomberg implemented a curfew to prevent clashes and deployed more police units. Meanwhile in Washington DC, Congress was debating whether or not to deploy the National Guard to Alaska to prevent a Russian invasion, or use the soldiers in Taiwan. The Taiwanese ambassador to the US demanded that all available military units be moved to defend the Republic of China.
Outside the Pentagon, anti-war and pro-war demonstrators clashed, leading to five casualties and over thirty injured. Riot police broke it up using tear gas and rubber bullets. The protesters threw firebombs and rocks at the police, damaging a SWAT van and several police and civilian vehicles. Over one hundred were arrested for disturbance of the peace and assault, while security was increased.
The next day, the Russian government announced it was expelling all US citizens and diplomats on persona non grata charges and claimed that they were spying. That afternoon, they recalled their earlier statements and allowed the diplomats to stay.