Secretary of State Mike Pompeo’s announcement on Friday that the United States is suspending the Intermediate-Range Nuclear Forces Treaty should worry everyone. The I.N.F. is a landmark treaty and it has made the world a safe place. It was the first nuclear agreement to ever outlaw an entire class of weapons.

The Trump administration has dismissed the I.N.F. as irrelevant because Russia has abrogated its commitment to it by developing a treaty-busting cruise missile of its own. The Russians, for their part, claim that it is the United States that started this race to the bottom by announcing its withdrawal from the Antiballistic Missile treaty in 2001 and building missile defense systems near Russia’s borders. Regardless, it should be kept in place.

The turn away from arms control agreements is not happening in a vacuum. The National Nuclear Security Administration, the part of the Department of Energy that oversees weapons production, announced this week that it has begun production of a new low-yield nuclear weapon that is about one-third as powerful as the bomb used on Hiroshima. These bombs are considered by some “small enough to use.” It could be ready for deployment by the end of the year.

Welcome to the new age of nuclear instability. This is a perilous time in which agreements that have restrained the most dangerous weapons on the planet are dissipating and threatening new technologies — including cyberweapons that could attack nuclear command and control systems — are advancing quickly. The likelihood of a nuclear accident or blunder seems to be growing by the day.