During the long years of the Cold War from 1945 to 1991, the U.S. and the former Soviet Union faced off against each other, both having an arsenal of nuclear weapons. Only once, during the Cuban missile crisis in October 1962, did the prospect of a real threat to the homeland arise. After a U.S. naval blockade was imposed, the Russians took their missiles home.
The key factor was that the Russian leaders were not suicidal. They were not crazy. They fully understood what it would mean to actually use nuclear weapons or be on the receiving end of them.
The Iranian ayatollahs are a different case entirely. Over the years, they have voiced a rather nonchalant attitude toward being on the receiving end of nuclear weapons because they are a Shiite martyrdom cult. During its eight-year war with Iraq, initiated by Saddam Hussein, an estimated 500,000 Iranians died, including 100,000 children sent to clear mine fields by setting them off.
The failure to grasp the depth and insanity of the current leaders of Iran is pushing the world toward the first nuclear confrontation since A-bombs were dropped on Nagasaki and Hiroshima to end World War II in 1945.