Most major war in YN's history

[The New Cordian Empire]

What was the most major war in YN's history? Who were the combatants, what were the major battles, and who won?

Mine: The Cordian Revolution. Combatants: The Cordian Empire, The New Cordian Army. Later, The New Cordian Army, South Cordia, and West Cordia. Major Battles: Battle of Tunripita, Battle of Aeravanum, Battle of the Verulania, Battle of Pavendumsa. Winners: The New Cordian Army and West Cordia.

[Nationalistic United Korea]

The most important war of Korean history is likely too common to irl so let's do the second most important.

Fatherland Unification Liberation War(known as the Second Korean War)
Dates: From 1961- 1965
Belligerents: Republic of Korea and Japan Democractic People's Republic of Korea and Chinese aid
Events: With DPRK raids into the ROK many felt the north was trying to invade again. After an attempt on Park Chung-hee's life ROK forces offically crossed the 38th Parallel. Within weeks P'yongyang had fell and the ROK proved a worthy army until Chinese aid grinded the war to a bloody stalemate. Most of the war remained like this until Japan's entrance and the Chinese withdrawal ending the war with ROK victory.
End Result: 3 million dead mainly ROK forces, Unification of Korea under an anti communist military Dictatorship, easing of Korean-Japanese relations.