Manchuria-North Korean War

I think I'll start with a war during the 1990s. Manchuria's communist government, a more pro-Soviet state, collapsed at this point. In this version's Korean War, the Chinese still help the North Koreans at that time, it's just that Manchurians also helped as well. The result is still basically the same.

Basically, the Manchus tried to impose the original Manchu language (in the former Manchukuo, the Manchurian language being talked about is the Manchurian Chinese dialect and the Communist government made it ambiguous), but they only succeeded in making first speakers among the ethnic Manchu minority; the rest speak it as a second language. It's the same situation as in OTL Philippines, where Tagalog and other languages are spoken, but the language of government and media is in English. Most of the Han population still speaks Chinese, but it's now a Singapore-like situation; the language of the majority is Chinese, but the language of the government, the economy, and the media is largely Manchu now.

During the Sino-Soviet split, the Manchurians sided with the USSR against China. North Korea is still technically neutral but leaned more towards China; however, it went neutral again after Deng took power. Chinese-Manchurian clashes are like OTL India-Pakistan wars; pointless border wars with heavy casualties.

In the 1990s, North Korean refugees swarmed Manchuria during a famine. Manchuria took them as a way to reduce the Chinese population of Manchuria, a cynical move by Changchun. Kim Jong-il was angry and decides to invade Manchuria. He didn't care that Manchuria has nukes; he is told he's three months away with the nukes and the Manchurian Army was demoralized after their wars in South-east Asia (e.g. helping Vietnam during its invasion of Cambodia). Unfortunately for him, the NK invasion pissed off the Manchus more and threatened the North Koreans nukes if the North Koreans persist on launching gas attacks they are doing against border cities. China tried to help NK and launched another skirmishes against the Manchus, but were forced to back off when a Chinese ship was accidentally sunk by a North Korean sub. 

Because the NKs are not persistent, the Manchus launch an mobile IRBM strike against suspected and real North Korean cities, the first nuclear strike since the Second World War. They actually managed to wipe out the North Korean nuke program by pure luck, a former NK defector said. While none of the major North Korean cities were hit by the "Five Suns", as it was called, 

With their ace gone, the North Koreans ended up in a civil war while the Manchurians decide to finish the job, Chinese retaliation notwithstanding. A ceasefire was reached by China and Manchuria in exchange for China not intervening against North Korea. Manchuria allowed China to receive North Korean exiles as well. In a winter offensive, Manchurians reached Pyongyang by March 1, 1995, and used their best gendarmerie troops in house-to-house combat instead of the motorized infantry and armored divisions they rolled out against regular North Korean line formations. The brutality of both the North Korean defenders and the Manchu gendarmes were shown on live TV, but in the end, the March 20 Aum attack turned Japan even more against North Korea, seeing it as a North Korean plot even if the cult Aum Shinrikyo was really behind it-they received North Korean funding and instructions. South Korea on its part, while at first apprehensive, later asked the Americans to save Pyongyang from the Manchus; as much as they hate the North Korean regime, they could not allow the "braided, barbarian Manchus" to occupy a Korean city, and rolled their own troops with Clinton's permission to engage North Korean troops and possibly force the Manchurians to withdraw.

When the fighting died down on August 9, 1995, the South Koreans occupied the South of Pyongyang, while the Manchurian occupy the North. North Korean guerrillas are still active, but were progressively wiped out, which earned foreign criticism for their severity; Manchurians defended it as "fighting fire with fire". Kim Jong-il was captured by Manchurian special forces and were handed over to South Korea. 

Protracted negotiations by Changchun and Seoul for the turnover of NK to Seoul were long, and the subject of disputes; the OTL 1997 financial crisis was triggered earlier for obvious reasons; the IMF helped the Republic of Korea, which is now viewed as the successor state of North Korea, knowing that they can't risk a worse financial meltdown. 

In Changchun, the Manchurian National Assembly were fighting towards the future of North Korea; the conservative candidate for Prime Minister wanted to annex North Korea and turn it into an "extractive territory" for war reparations; however, a liberal candidate demanded that the Manchus withdraw, as they have suffered too and need rebuilding; annexing North Korea he said, is petty and will cause more wars with both Beijing and Seoul. When the Liberal candidate's party won, the conservatives tried to launch a coup de-etat with their armed supporters, but the majority of the military, the people, and the police sided with the Liberals, claiming that the Manchurians won and need to go home now. (Basically a January 6 but with Soviet August Coup attempt). After that, the new Manchurian leader negotiated with Seoul and promptly declared that the Manchus will leave North Korea by December 1998 and hand over the territory to the Americans and Seoul. 50 kilometers from the Yalu River was to be the new boundary limit for the US forces. A ceremony by surrendered North Korean officials and Seoul formally reunified the country with little fanfare.

By then, most North Korean terrorism stopped to OTL Northern Ireland or Chechnya levels as both the Republic of Korea and the Republic of Manchuria rebuilt their lands. Most of Pyongyang today resemble Busan and Seoul as of OTL; with some vibes of Grozny. There are still tensions with Changchun and Seoul, but for the most part, it's confined in 4chan and politics.