How the fuck did two socialist countries split up and ultimately come to the brink of nuking each other? I thought that socialism was supposed to abolish war? What the hell happened?
Sino-Soviet Split
The USSR, or rather Russia, wanted to be the leaders of effective overlords of new socialist states. China had the potential to rival them in power and stood up to them with their minority differing ideology.
Also interested. I know very little about it but from what I understand, Stalin administration foreign policy was in contradiction with Mao's foreign policy. Not exactly sure how, Stalin was definitely a bit strange on his socialism in one country whether or not your coming from a sympathetic angle towards him or not. Instructing communists not to hold revolutions in their countries until they recieved Soviet approval and trading Greece to Britain, focusing so much on promoting parties that shared the Stalinist line over even more viable possibilities, etc. I'm sure it was more complicated than this and I'm far from clear on the history but it seems like strange mismanagement.
Yeah basically I'm seconding OP in the "what the fuck happened here"
From what I know about greece stalin didn't want to do much about it because a possible conflict with US would be mad seeing the state of russia after the war + USSR didn't have a navy.
There were all sorts of motives, namely:
1. Mao had distrusted the USSR's "older brother" relationship with China, which included refusing to help the Chinese acquire nuclear weapons, Mao's fear that a US-USSR accord would involve "selling out" China, and also nationalist disputes over borders and over Mongolia (which Mao claimed the Soviets snatched away from China.)
2. Mao thought Stalin had a mechanical understanding of Marxism, but that Khrushchev and his successors were revisionists who restored capitalism in the USSR.
3. The Great Leap Forward and Cultural Revolution were denounced by the USSR as anti-Marxist, whereas Mao saw opposition to them within China as the work of "capitalist roaders" seeking to overthrow him and restore capitalism. It's why Liu Shaoqi was attacked as "China's Khrushchev."
So yeah part of it was nationalism, part of it was ideological differences, part of it was Mao's own personal standing within the international communist movement and at home.
Sources giving the Soviet side: revleft.space
Sources giving the Chinese side: bannedthought.net
The USSR and China did eventually start patching up relations from about 1982 onward, as Deng no longer claimed the CPSU had "restored capitalism" (but still criticized its foreign policy) and as the Soviets saw that Deng clearly wasn't pursuing anything that could be considered remotely ultra-left inside China.
Issues always existed between them such as the fact that Mao didn't want china to be seen as a vassal state of the USSR such as how the Warsaw Pact / CMEA States were perceived
This was compounded by the fear of Soviet troops on their border in both USSR and Mongolian territory (This was the main reason the USSR never included Mongolia in the WP) and increased even further with the Soviet intervention in Afghanistan
Relations deteriorated to their worst during Nikita's tenure and its immediate fallout (60s-Early 70s) when China accused the USSR of "Restoring Capitalism" and entered a "Defensive alliance" with the US and several other NATO states against them
Once Deng came to lead China in the late 70s-80s he attempted to somewhat rebuild the relationship (The PRC stopped openly calling the USSR Capitalist / Social-Imperialist in propaganda etc) but very little was accomplished before Gorbachev was elected and hit the self destruct button
Megalomaniac dictators dont always get along, the end.
Short answer. When Khrushchev took power, Mao calles him a revisionist and the two hated each other ever since.
It's interesting – you will still see Xi Jinping reference Stalin in party Congress speeches.
Stalin had to kill the revolution in order to save the revolution. Everything that followed would inevitably fall horribly short of socialism's intended goals.