'Today, after nearly five years of war, and 22 months of the second Trump administration, the mental map guiding Russian strategy has changed. First, Russia now sees Europe, instead of the United States, as its principal geopolitical adversary, a shift that has driven Russia’s defense establishment to call for an approach known as “castling” to deal with the main threats. Related to this, Moscow now attributes new strategic agency to Europe itself because of the dramatic military modernization taking place in many European countries and the growing interest among some European leaders in developing or extending their own nuclear deterrent. A third shift concerns Russia’s theory of deterrence: Moscow’s traditional understanding of nuclear coercion is giving way to new thinking about nonnuclear strategic deterrence using advanced conventional weapons systems aimed at Europe. ... One of the most notable trends in Russian strategic thought over the past year has been the emergence of the idea of “castling.” A term borrowed from chess, castling in geopolitics describes the repositioning of forces and resources to optimize a state’s strategic posture. Moscow’s defense experts have used the concept to describe a strategy for dealing with a new reality: for the first time since World War II, they have argued, Europe, rather than the United States, has become Russia’s principal geopolitical adversary. According to this view, European countries are now the principal source of Ukraine’s military capacity, political resolve, and strategic resilience; it is Europe and not the United States that has made Ukraine its proxy and is encouraging Kyiv to pursue Moscow’s strategic defeat. As a consequence, Moscow must direct coercive pressure at Europe—its elites, its decision-making centers, and its critical infrastructure. By doing so, Russia can instill into Europe’s calculus what theorists in Moscow call a “deterring fear”: a European reluctance to antagonize Russia through further support to Ukraine. Such action, they argue, can also rebuild Russian credible deterrence for long-term competition with the West, which is now centered on Europe. .... Drawing on this experience, Russian military theoreticians center NNSD on using massive, deep, precision strikes against the adversary’s critical military, political, and economic infrastructure. The strategy, they suggest, should be aimed not only at Ukraine but also at its European supporters. Although the exact contours of NNSD are still emerging, the concept appears to be more escalatory than the hybrid warfare and deniable asymmetric campaigns that Russia is currently pursuing in Europe.'