The era of nuclear arms control officially ends this week. On Feb. 5, New START, the last such treaty between the United States and Russia, will expire. That doesn’t necessarily mean that Washington and Moscow will begin deploying more than the 1,550 strategic warheads each that the treaty stipulated; both of them should and probably will observe the old limits for a while longer. Nonetheless, the moment is a milestone.

It marks the first time since the iciest days of the Cold War when no formal arms-control regime will limit the two atomic superpowers. In that way the expiry of New START is yet another step out of a world in which the great powers restrained themselves with rules and into a brave new world of anarchy, in which the only rules are the whims of strongmen.

On paper, a few vestiges of the previous era remain. Some 178 countries still abide by a multilateral treaty that bans the explosive (as opposed to computer-simulated) testing of fission or fusion bombs. And 191 states still subscribe, in theory, to The Treaty on the Non-Proliferation of Nuclear Weapons (abbreviated NPT), in force since 1970. The signatories include the five powers with the largest nuclear arsenals, who in Article VI explicitly commit to negotiate “in good faith” to achieve “general and complete disarmament.”