It's pretty easy to find sources about Russia's invasion of Afghanistan. Here is the article in Britannica.

Soviet invasion of Afghanistan, invasion of Afghanistan in late December 1979 by troops from the Soviet Union. The Soviet Union intervened in support of the Afghan communist government in its conflict with anti-communist Muslim guerrillas during the Afghan War (1978–92) and remained in Afghanistan until mid-February 1989.

Also in Britannica:

The Brezhnev Doctrine severely limited reforms by Soviet-bloc countries in the ensuing decades. In addition, it was used to justify the Soviet invasion of Afghanistan in 1979. The Soviets sought to prop up the country’s communist government in its battle with anticommunist Muslim guerrillas.

Russia is certainly not the ONLY major power which has a doctrine justifying invasion. We Americans have the Monroe Doctrine, for one. But if you'd care to explain how Russia is still a leader for peace while using their Brezhnev Doctrine to justify a decades long invasion, I for one am all ears.