The Korean War was a military conflict fought between China and the Anti-Wario Alliance. It was fought because Wario was being a jerk in a bunch of countries and then China was hiding him. There were over 3,000,000,000,000 estimated casualties during the war (that's a lot for the 1600s). Despite the name, no fighting actually took place in Korea.
It all started when Wario challenged Mario to a sumo match. Mario agreed, and then cheated by using a starman. Wario was banished from the Mushroom Kingdom, so he began to travel. During this time, he seriously pissed off Sparta and the Squadala Empire. Realizing they wanted him dead, he went to China where they welcomed him. After a few years, Wario managed to get high up in the Chinese government. That's when the Anti-Wario Alliance was formed and war began.
Battle of West China
The first battle of the Korean War was the battle of West China. The Squadala Army ran in screaming. All the Chinese guys shot all the Squadalan guys dead, and the Squadalan guys ran for their pathetic lives. But then a bunch of Toads from the Mushroomian army attacked and won the battle.
Battle of Central China
After the Battle of West China was won, the 300 pushed the attack further. They pushed it all the way back to Central China, where the Spartan guys attacked the Chinese guys. The Chinese guys almost won, but then Morshu sold Leonidas lotsa bombs for lotsa rupees. These bombs made Central China asplode.
Battle of East China
Eventually the 300 pushed the Chinese guys all the way to the ocean, where the Toads came in and ate the Chinese guys. Squadala Man declared that the Squadala Empire had won the war (even though the Squadala Army didn't accomplish squat), and the Chinese guys were to hand over Wario or be blown up by more bombs. China surrendered to the Squadala Empire shortly afterwards.
Right after China surrendered, Morshu sold China lotsa bombs. China had 9001 times the bombs Leonidas used on China. This made China the most powerful country in the entire UnWorld. Nobody knows how Morshu even got so many bombs. But Everybody agreed to pretend none of this ever happened, and China gave Wario some of its land which is now called North Korea.