BRUSSELS—U.S. Defense Secretary Jim Mattis said on Oct. 4, that Russia’s violation of an arms control treaty was “untenable” and unless it changed course the United States would respond.
The United States believes Russia is developing a ground-launched system in breach of a Cold War treaty, known as the Intermediate-Range Nuclear Forces Treaty (INF), that could allow Moscow to launch a nuclear strike on Europe at short notice. Russia has consistently denied any such violation.
