A year after Russia’s full-scale invasion of Ukraine, contrary to most forecasts, Russian territorial gains are practically minimal, and Ukrainian military resistance continues to this day. Despite the support they have received so far from the West, the Ukrainians need more equipment. The Commander-in-Chief of the Armed Forces, Valery Zaluzny, during our meeting in Kyiv, when asked what else his troops need, unbuttons his khaki jacket, revealing a T-shirt with the inscription “F-16!”. Next on his list, after combat aircraft, are long-range missiles such as the US ATACMS, which allow forward troops to hit Russian targets beyond the range of their current weaponry.

When talking to Mr. Zaluzny, the first thing you realize is that these demands are not just rhetoric, but an urgent military necessity, and that Zelensky’s visit to London, Brussels and Paris, during which the Ukrainian president urged planes, reflects an urgent fact: the next six months will become a period of “life and death” for Ukrainians. After all, in any war the fundamental question is: “Which side is time on?” In 1942, so to speak, time was on the side of the Allies. Today, as a Sino-Russian military partnership is being planned, many fear that time is running out in Vladimir Putin’s favor, and he probably thinks so too.

But the question asked and answered by those who help Ukraine militarily is: “How will these weapons be used?” For most in the West, the answer to this question lies in Crimea. It’s no secret that one of Ukraine’s strategic plans is to launch a major counter-offensive in the south of the country in the spring, especially around Kherson and Zaporozhye, which, if successful, will push Russian troops back to the borders of Crimea. And here comes the great dilemma. Almost all Ukrainians I have met are in favor of the return of Crimea. Their arguments are cultural, historical, political and legal. But they are also strategic. In the long run, they argue, security in Ukraine is impossible while Russian troops are encamped in Crimea. I was told that at the moment Russians are more interested in Crimea than in Donbass. A possible push from the peninsula, with the simultaneous destruction of the Kerch bridge by long-range missiles, would probably force Putin to the negotiating table.

Zelenskiy’s call for aircraft reflects a vital fact: the next six months will be a period of “life or death” for Ukrainians.

This makes strategic sense, but it also comes with a lot of risk. Most decision-making centers in the West believe that Ukrainians should stop in Kherson for the same reason they want to take it: because it is of great importance to Russia. They fear that an attempt to retake Crimea could provoke a strong Russian response, including the use of tactical nuclear weapons. This is one of the reasons why the US refuses to provide aircraft to Ukraine.

But there is no choice without risk. How dangerous is the attempt to return Crimea and the promises of the West to grant Ukraine membership in the EU. and in NATO, it is so dangerous to drag out the war for years and manage to reach an agreement between Vladimir Putin and Xi Jinping. And this second risk is greater. We must have the courage and wisdom to recognize this. And fear is a very bad adviser. In his speech on Tuesday, Vladimir Putin made it clear that he was trying to intimidate the West. Let’s not let him get away with this.

* Mr. Timothy Garton Ash is Professor of European Studies at the University of Oxford.