The Soviets sent troops into Afghanistan after Muslim fundamentalists opposed the efforts of a newly elected Afghan socialist president to create a country where women could vote and attend school.  This was perceived as an attack upon Islam, and they started fighting the Afghan army.

At first the Soviets supported the Afghan army, trained it and supplied it.  The citizens of the USSR were told they were building schools, hospitals and libraries, distributing food and supplying medical care.  (Comment:  Does that happy horseshit sound familiar?)   Eventually the Soviets had to take over the fighting.

The various outside organizations who supported the fundamental Muslims, Saudi Arabia being the most generous, and the US significant, funneled their contributions through Pakistan.  For their own reasons the Paks gave most of the aid to the most fundamental sects.  After some years the public pressure on the government from Russian citizens forced the Russians to try to find a way out without looking like the Americans in Vietnam.

Gorbachev met with Reagan to try to create a coalition Afghan government the US wouldn’t supply.  The UN brokered the Geneva Accords, which would have brought peace. Reagan, seeking revenge for Vietnam, kept urging the Muslims on, and increased the supply of weapons.  Both sides then ignored the accords and the Russians started withdrawing anyway.

The war continued with Afghans fighting Afghans, using American and Soviet weapons.  The entire thing was regarded as a total waste by the Russian people.

Comment:  The US could have learned from the Russians in Afghanistan who could have learned from the Americans in Vietnam.  But no one learned, and now the US is back in Vietnam fighting the fundamentalist Muslim they once supported so that women can go to school, vote, etc.