The international arms control architecture is eroding. After the United States’ withdrawal from the joint comprehensive Plan of Action with Iran in 2018 and the abrogation of the Intermediate-Range Nuclear Forces Treaty (INF) in 2019, this year saw another major blow against a key agreement, the Open Skies Treaty (OST). Secretary of State Mike Pompeo announced on May 21st that the Trump administration decided to leave the treaty with a notice period of six months.