What happens now after Russia suspends the last nuclear arms treaty with the U.S.?

A woman in Simferopol, Crimea, watches a TV broadcast of Russian President Vladimir Putin's annual state of the nation address on Tuesday. Putin announced Russia is suspending participation in the New START nuclear weapons treaty. (AFP via Getty Images)

In 1985, Soviet leader Mikhail Gorbachev and U.S. President Ronald Reagan made a breakthrough when they jointly declared, "a nuclear war cannot be won and must never be fought."

That phrase has lived on, evoked by leaders of both countries. It was affirmed as recently as January 2022, by Russian President Vladimir Putin, President Biden and the leaders of China, France and the U.K., all of which have nuclear weapons and permanent seats on the U.N. Security Council. But the following month, Putin launched a full-scale invasion of Ukraine, and Russia used nuclear threats in an attempt to intimidate other nations from intervening.