President Trump’s decision today to withdraw from the Iranian nuclear deal is a major strategic mistake that not only damages the United States’ ability to prevent Iran from acquiring the material for a nuclear weapon, but also impairs our ability to prevent the spread and use of nuclear weapons, to work with allies and partners on issues of global concern, and to protect our interests in the Middle East for years, if not decades, to come. The Iran nuclear deal rolled back Iran’s nuclear program and imposed uniquely stringent monitoring and verification measures — the most important elements of which were permanent — to prevent the country from ever developing a bomb. The United States is now in violation of the terms of the deal without offering a credible alternative. The Iran deal is and has always been about depriving Iran of the nuclear materials — highly enriched uranium and plutonium — needed to make a weapon. As international inspectors, who have been on the ground every day since the deal was concluded, have confirmed: The Iran agreement has accomplished this. The fact that the advice of this nation’s most-important allies was ignored in this decision adds to the consequence of the president’s decision. Remaining in the agreement was very clearly in the U.S. national interest. It’s hard to predict what will unfold from here, but the president has driven a deep wedge between the United States and our allies in Europe and has withdrawn from the process that would allow a comprehensive investigation of the Iran archives recently revealed by Israel.