The last remaining nuclear arms pact between Russia and the United States is set to expire this week, removing any caps on the two largest atomic arsenals for the first time in more than a half-century.

Nearly 100 former senior U.S. diplomats and intelligence and national security officials have asked Senate leaders to schedule closed-door hearings to allow for a full review of the government’s files on former Rep. Tulsi Gabbard.

Russia’s assault on Ukraine and its veiled threats of using nuclear arms have policymakers past and present thinking the unthinkable: How should the West respond to a Russian battlefield explosion of a nuclear bomb.