'Quietly and under a shadow of unease, the Trump administration is opening the door to U.S. resumption of underground nuclear explosive testing. Anyone familiar with the directive and the test-ban treaty negotiating record would understand how completely misleading this is. If the president follows his national security team into this dark room, it could shatter the 50-year international consensus behind preventing the spread of nuclear weapons and launch a new nuclear arms race. Why would the Trump administration seek to restart nuclear testing? In March, four Republican senators wrote the president asking whether he would consider “unsigning” the CTBT, calling the pact a “deeply flawed treaty that purports to ban all nuclear weapons tests.” The seemingly out-of-the-blue letter from Republican senators and the DIA director’s public remarks had the look of an orchestrated campaign .'