what you need to know

For a brief period, Ukraine was the world’s third-largest nuclear power. The dissolution of the Soviet Union in December 1991 left Ukraine with a large nuclear arsenal — about 1,900 strategic nuclear warheads designed to strike the U.S. and 2,500 shorterrange nuclear weapons. But it gave up all those nuclear warheads in return for a 1994 promise from the U.S. and Russia not to use force or threaten military action against the newly independent nation — the so-called Budapest Memorandum on Security Assurances. The Budapest agreement was considered a major diplomatic accomplishment two decades ago, when the U.S. and Russia shared an interest in limiting the number of nuclear-armed states and reducing the risk that former Soviet weapons would fall into the wrong hands. Bloomberg News