Why was Afghanistan known as the Soviet Union's Vietnam?

It is called their vietnam war cause it is in many ways similar to what america faced in the 1960's and the early 1970's in vietnam

The Soviet Union provided support to the Communist Vietnamese via weapons and supplies ... Finally Soviet Union decided to withdraw its troops from Afghanistan and ended the war. It is called their Vietnam War because it is in many ways similar to what America faced in the 1960's and early 1970's in Vietnam.