Why was the afghan war called the Vietnam of the Soviet Union

The first CIA-supplied weapons were antique British Lee–Enfield rifles shipped out in December 1979 by September 1986 the program included U.S.-origin state of the art weaponry, such as FIM-92 Stinger surface-to-air missiles, some 2,300 of which were ultimately shipped into Afghanistan. Funding officially began with $695,000 in mid-1979, was increased dramatically to $20–$30 million per year in 1980, and rose to $630 million per year in 1987, described as the 'biggest bequest to any Third World insurgency'. Operation Cyclone was one of the longest and most expensive covert CIA operations ever undertaken. The program leaned heavily towards supporting militant Islamic groups, including groups with jihadist ties, that were favored by the regime of Muhammad Zia-ul-Haq in neighboring Pakistan, rather than other, less ideological Afghan resistance groups that had also been fighting the Soviet-oriented Democratic Republic of Afghanistan administration since before the Soviet intervention. The mujahideen were also supported by Britain's MI6, who conducted their own separate covert actions. Operation Cyclone was the code name for the United States Central Intelligence Agency (CIA) program to arm and finance the Afghan mujahideen in Afghanistan from 1979 to 1992, prior to and during the military intervention by the USSR in support of the Democratic Republic of Afghanistan. 1979–1989 Afghanistan, Operation Cyclone.1965–66 Indonesia, Transition to the New Order.1959–2000 assassination attempts on Fidel Castro.Collapse of the Democratic Republic of Afghanistan in 1992.Soviet withdrawal from Afghanistan in February 1989.Delivery of thousands of tons of weaponry worth several billion US dollars.Government of Afghanistan and USSR invasion force

Why was the afghan war called the Vietnam of the Soviet Union