The invasion stemmed from a massive deterrence failure

• Russia decided to invade only to be surprised by the scope and intensity of the West’s responseAs Nato military chiefs meet in Brussels to discuss the war in Ukraine, the other issue on their minds is the alliance’s forthcoming Strategic Concept, which will shape its priorities for years to come. And here, Russia’s behaviour has demonstrated that re-establishing deterrence must play a central role.When Russia began amassing troops on Ukraine’s border late last year, it embarked on a path of aggression against not just Ukraine but also what it calls the “collective West,” particularly the European Union and Nato. Russia was seeking to deter Ukraine and the West from increased collaboration, while the West was seeking to deter Russia from aggression. The subsequent invasion stems from a massive failure of deterrence. The Ukrainians have marshalled an impressive defence, and the EU, Nato, and other Western partners and allies have continued to tighten economic and financial sanctions and provide aid. But we are in a dangerous cycle of escalation. The situation demands credible deterrence that goes far beyond the traditional “nuclear umbrella.”After all, deterrence is not only about nuclear warfare. It is relevant to all forms of confrontation – whether in business or on the battlefield. Many of these dynamics are present in the current conflict. Russia and Europe’s codependent energy relationship had been deemed a strong deterrent on both sides; but it patently failed.Deterrence is about convincing an opponent that not doing something is in its best interests. Russia first attempted to deter Ukraine and the West by deploying its troops along Ukraine’s borders. But as it did, the United States and its Nato allies released daily intelligence and data revealing Russian troop movements, demonstrating clearly to the Kremlin that they knew what it was doing. Such signalling is the first element of deterrence.Another core element of deterrence is the belief that an adversary has both the will and the capability to escalate measures if the other side does not change course. When Russia issued a litany of demands designed to highlight Ukraine and Nato’s vulnerabilities – from Ukraine’s status as a state to the overall European security architecture – its audience didn’t find its threats to be credible.With the exception of the US, few believed that Russia would launch a full-scale invasion or persist with its threats against Nato and neutral states. Yet Russia did invade and has since issued veiled nuclear threats and even tested a new supersonic missile.Similarly, Russian President Vladimir Putin did not take seriously French President Emmanuel Macron, German Chancellor Olaf Scholz, and other Western leaders when they expressed their intentions to support Ukraine. The Kremlin heard these statements, but it also heard several other leaders, including US President Joe Biden, say that they would not send troops to defend a non-Nato country. Russia thus decided to invade, only to be surprised by the scope and intensity of the West’s response. For its part, Ukraine’s deterrence strategy was essentially to project an image of itself as a country that already belonged to the West. And though the Kremlin was unpersuaded, Russia clearly underestimated Ukrainian unity and the capability and competence of its army, even though it had been fighting Ukrainian forces since its incursions into the country in 2014.Ukraine’s heroic self-defence reminds us that beyond the battlefield and business, beyond sanctions and institutions, there are ordinary people: the war is taking place among them, and they will decide its ultimate outcome. Though Ukrainians’ will to defend their lives, homes, and ideals has not yet deterred Russia’s leadership, there is strong evidence that it has deterred many Russian soldiers from fighting.Looking ahead, Western deterrence must become a primary strategic objective and thus more comprehensive, including all the elements that matter. US Secretary of Defense Lloyd Austin took a step in this direction by announcing that one of America’s goals now is to “see Russia weakened to the degree that it can’t do the kinds of things that it has done in invading Ukraine.” And the $33bn lend-lease bill that Biden signed on May 9 will further advance this goal.But it’s not enough. Deterrence must be a popular aim that commands widespread public support. It also must be backed by other countries, because international cooperation is crucial for ensuring the security of smaller, vulnerable states. Achieving such broad-based support requires effective, inspirational leadership of the kind that Ukrainian President Volodymyr Zelensky has demonstrated. He has rallied not only the Ukrainian people but the entire Western world. Other leaders would do well to follow his example.Finally, it is important to remember where deterrence fits in the broader context of globalisation. Russia was emboldened by the economic interdependencies that it has cultivated, and it was empowered by its status as a permanent, veto-wielding member of the United Nations Security Council. Deterrence must include measures either to neutralise or contain both factors.The war in Ukraine is the result of insufficient deterrence. Ultimately, there will be no peace without it. — Project Syndicate• Rupert Smith is a former Nato deputy supreme allied commander for Europe. • Ilana Bet-El, a strategist and historian, is a senior associate fellow at the European Leadership Network.