The natural results of profound stupidity; i.e. post-Soviet invasion Afghani guerillas who figured out how to drive a Soviet APC, but never thought that other post-Soviet Afghani guerillas might figure out how to work an anti-tank weapon.
(this is sometimes erroneously cited as either a Russian APC being blown up in the insurgence in Chechnya, or as a US Special Forces unit being blown up in the 2002 conflict in Afghanistan. It's one bunch of camel-fvcking warlords blowing up another bunch of camel-fvcking warlords, rest easy.)