In return for Mr Zelensky embracing this grim truth, Western leaders need to make his overriding war aim credible by ensuring that Ukraine has the military capacity and security guarantees it needs. If Ukraine can convincingly deny Russia any prospect of advancing further on the battlefield, it will be able to demonstrate the futility of further big offensives. Whether or not a formal peace deal is signed, that is the only way to wind down the fighting and ensure the security on which Ukraine’s prosperity and democracy will ultimately rest.

This will require greater supplies of the weaponry Mr Zelensky is asking for. Ukraine needs long-range missiles that can hit military targets deep in Russia and air defences to protect its infrastructure. Crucially, it also needs to make its own weapons. Today, the country’s arms industry has orders worth $7bn, only about a third of its potential capacity. Weapons firms from America and some European countries have been stepping in; others should, too. The supply of home-made weapons is more dependable and cheaper than Western-made ones. It can also be more innovative. Ukraine has around 250 drone companies, some of them world leaders—including makers of the long-range machines that may have been behind a recent hit on a huge arms dump in Russia’s Tver province.

The second way to make Ukraine’s defence credible is for Mr Biden to say Ukraine must be invited to join NATO now, even if it is divided and, possibly, without a formal armistice. Mr Biden is known to be cautious about this. Such a declaration from him, endorsed by leaders in Britain, France and Germany, would go far beyond today’s open-ended words about an “irrevocable path” to membership.

This would be controversial, because NATO’s members are expected to support each other if one of them is attacked. In opening a debate about this Article 5 guarantee, Mr Biden could make clear that it would not cover Ukrainian territory Russia occupies today, as with East Germany when West Germany joined NATO in 1955; and that Ukraine would not necessarily garrison foreign NATO troops in peacetime, as with Norway in 1949.

NATO membership entails risks. If Russia struck Ukraine again, America could face a terrible dilemma: to back Ukraine and risk war with a nuclear foe; or refuse and weaken its alliances around the world. However, abandoning Ukraine would also weaken all of America’s alliances—one reason China, Iran and North Korea are backing Russia. Mr Putin is clear that he sees the real enemy as the West. It is deluded to think that leaving Ukraine to be defeated will bring peace.

Indeed, a dysfunctional Ukraine could itself become a dangerous neighbour. Already, corruption and nationalism are on the rise. If Ukrainians feel betrayed, Mr Putin may radicalise battle-hardened militias against the West and NATO. He managed something similar in Donbas where, after 2014, he turned some Russian-speaking Ukrainians into partisans ready to go to war against their compatriots. For too long, the West has hidden behind the pretence that if Ukraine set the goals, it would decide what arms to supply. Yet Mr Zelensky cannot define victory without knowing the level of Western support. By contrast, the plan outlined above is self-reinforcing. A firmer promise of NATO membership would help Mr Zelensky redefine victory; a credible war aim would deter Russia; NATO would benefit from Ukraine’s revamped arms industry. Forging a new victory plan asks a lot of Mr Zelensky and Western leaders. But if they demur, they will usher in Ukraine’s defeat. And that would be much worse