Actually WWII in general might qualify for this. I mean WWII starts with Japan going to war with two Chinese factions, both of which spend as much as or more time fighting each other as they do fighting the Imperial Japanese Army. It goes to Europe where the Soviets and Nazis are allies in the first two years of the war, Poland is a military dictatorship subject to Nazi aggression. France, Poland, Yugoslavia, Greece, all of them have convoluted military histories, what with the Vichy/Free French/French Communist Party triumvirate in France, the Warsaw and Lublin Governments in Poland, the Ustaste-Chetnik-Titoist bunch in Yugoslavia, the Greek monarchists, republicans, and Communists, the Italian Salo Republic and the pro-Allied government, mixed in with the usual German "Kill All, Burn All, Loot All" approach to occupation.....
And this is without factoring in all the convolutions of Asian nationalism in WWII. Or for that matter the can of worms about whether the USSR (as I believe was indisputably the case) got away with nakedly absorbing three independent countries, whose nationalists during WWII were more anti-Semitic than the SS butchers themselves were, the RONA and its revealing the extent to which the Nazis were after all fanatical true believers, the whole convolutions of the Warsaw Rising, and the post-war Soviet Civil War that was written out of the history books.