The Warsaw Pact is envisioned to fight massive tank battles in West Germany. If victorious, a quick blitz would have easily overrun NATO powers France, United Kingdom, and Spain. Without European allies, the United States would probably a) sue for peace or b) end the world with nuclear strikes on the USSR.
When thinking about World War III many have thoughts of nuclear weapons and somesort of horrible post-apocalyptic wasteland. What many forget is that both NATO and the Warsaw Pact sought to win the war without the ending the war with mutually assured destruction. The Communists wanted to give a quick crushing blow while the West sought to inflict overwhelming losses while playing defense.
TechConex has American Department of Defense, probably Defense Intelligence Agency, produced maps which show what NATO expected in case of World War III. The Department of Defense (DoD) thought the main battle would be through the Fulda Gap. Here the technologically advanced NATO forces would face wave after wave of Warsaw Pact hardware ranging from modern to World War II antiques.
What is interesting is how the Soviets use geography to keep their opponents separate and too preoccupied to aid one another. The People's Republic of China is flanked on two sides, Alaska is invaded to tie down American forces, and the Middle East faces a direct assault then a swing attack via Asia Minor. It appears the DoD thought the Soviets hoped each front would face a singular, small enemy.
Who knows if these plans would have worked. Thankfully they never have been tested.