With a focus on the strategic competition between the United States and Russia, this paper explores the prospects for the future of arms control under an intensifying nuclear security dilemma. The end of stability-enhancing agreements such as the INF Treaty and Open Skies has accelerated the arms race. What is the future of New START and are we likely to see any extension beyond 2021? The relationship between arms control and strategic stability is part of this evaluation, particularly with respect to how states view the concept framed within their national security interests. The provocative role that offensive – deterrence by denial – capabilities play in contributing to strategic instability is central to this study. This work looks particularly at new systems designed for asymmetric advantage, including those that can defeat strategic defences, such as longer-range cruise missiles and hypersonic vehicles. Under conditions of modernizations and upgrades to nuclear arsenals, including the entanglement of conventional and nuclear systems that can threaten a first strike, this work considers how a dialogue on limiting dangerous systems could be initiated between the US and Russia. Could New START be revised – or a new treaty established – to limit advances in cruise missile technology, hypersonics, missile defences, and tactical nuclear weapons?