Peaceful co-existence of capitalism and socialism is a theoretical question of Marxism-Leninism, as well as a Khrushchevite slogan.
On the one hand, communist countries like the Soviet Union and People's Republic of China are defensive and do not attack capitalist countries unprovoked (despite what capitalist propaganda says).[1] Communist countries do not seek to "export the revolution" (unlike Trotskyists).
On the other hand, the bourgeois will not give up power peacefully, and communism's mere existence inspires their workers to rise up. So when they feel threatened by communism, especially as it grows materially stronger, they will either invade or carry out covert attacks against it. This happened throughout the entire existence of the Soviet Union.
For example, after the Bolshevik Revolution, Russia was immediately invaded by 10 countries. Then the British covertly funded the Basmachi terrorists in Central Asia. Then the Nazis and Japanese backed Trotskyist terrorists. Then the Nazis invaded the USSR. Then there was the Cold War.
After all this, Khrushchev still believed in peaceful coexistence. He used it as a slogan to advocate a rapprochement with the USA. However, the imperialists will not concede anything unless they get more in return, so Khrushchev capitulated to them on foreign policy. In the end, NATO still aggressed on the USSR, and Khrushchev was thrown out by Brezhnev for his failures in 1964.
- ↑ Stalin, Economic Problems, Ch. 6 Inevitability of Wars between Capitalist Countries. https://www.marxists.org/reference/archive/stalin/works/1951/economic-problems/ch07.htm