In 1942, Winston Churchill tried to ready the British people for a long conflict. “This is not the end,” he said, referring to the Allied victory in Egypt. “It is not even the beginning of the end. But it is, perhaps, the end of the beginning.” When we think in those terms, what phase are we witnessing in the war in Ukraine?

We are likely in the middle, explains Gideon Rose, a scholar at the Council on Foreign Relations and the author of an excellent book, “How Wars End.” He points out that every war begins similar to a chess game, with a dramatic attack and a defense. If those opening salvos do not produce a decisive victory, the war enters a middle phase, in which both sides try to slog it out to gain advantage on the battlefield. “During the middle phase,” he told me, “neither side is interested in negotiating because each side is trying to win outright, enhance their position on the battlefield, and thus have a stronger position from which to negotiate.” This is the period when emotions run high, making it hard to compromise.

Finally, at some point, the combatants enter the final phase through one of two paths: Either the tide of war turns irreversibly in one side’s favor (as happened in 1918 and 1944), or an exhausted stalemate emerges (as in Korea in mid-1951). “At that point, the parties enter the endgame, and they start jockeying over the final settlement,” Rose noted.

In this middle phase that we’re in, the West must help Ukraine strengthen its position. Kyiv needs more weapons and training. While there are real limits to how much the Ukrainians can absorb, Washington (and its allies in Europe and elsewhere) must redouble their efforts. They also need to help Ukraine break the Russian blockade around Odessa. People have focused on the collapse of the Russian economy, which will probably shrink by about 11 percent this year. But Ukraine’s economy is likely to contract by a staggering 45 percent in 2022. Unless the country can export its grain out of its Black Sea ports, it could face economic calamity for years to come.

Most likely, this middle phase of the war will last for a while. Neither Russia nor Ukraine has the capacity to win decisively, and neither is likely to surrender easily. In the short term, this favors Russia. It has taken control of much of Donbas. And because the West hasn’t completely banned Russia’s energy exports, the Russian government has actually profited during this war. Bloomberg projects Russia’s oil and gas revenue for this year will be about $285 billion, compared with $236 billion last year. Meanwhile, it can now thwart Ukraine’s ability to export. In the longer term, one has to hope that the sanctions will hit Russia harder as the war goes on. At the same time, Ukraine has massive Western assistance, high morale and a willingness to fight to the end.

Even though we’re not in the final stages yet, it would be smart for Ukraine to start thinking about the endgame. That way, it can develop a coherent position, align its strategy around it and gain international support. Former secretary of state Henry A. Kissinger was criticized for suggesting that Kyiv should not seek to go beyond the pre-Feb. 24 lines on the battlefield. In fact, at this point it appears highly unlikely that Ukraine would even be able to regain all that territory by force, though it should keep trying. But it does seem wise to make that its goal — to reverse Russia’s territorial gains from this year. Then Kyiv can try to get back territories lost before that in 2014 through negotiations. President Volodymyr Zelensky has several times suggested something similar. And that goal — a return to the pre-Feb. 24 lines — would also be one that would garner the most international support.

In the final phase of the war, the West — and the United States in particular — become the pivotal players. Right now Russia is battling Ukraine directly. But if and when the conflict becomes something of a stalemate, the real struggle will be between Russia and the West. What will Russia give to get a relaxation of sanctions? What will the West demand to end Russia’s isolation?

So far, Washington has punted on this, explaining that it is up to the Ukrainians to decide what they want and that Washington will not negotiate over their heads. That’s the right message of public support, but Ukraine and its Western partners need to formulate a set of common war aims, coordinating strategy around them, gaining international support and using all the leverage they have to succeed. The goal must be an independent Ukraine, in full control of at least as much territory as it had before Feb. 24, and with some security commitments from the West.

The alternative to some kind of negotiated settlement would be an unending war in Ukraine, which would further devastate that country and its people, more than 5 million of whom have already fled. And the resulting disruptions to energy supplies, food and the economy would spiral everywhere, with political turmoil intensifying across the globe. Surely it is worth searching for an endgame that avoids this bleak future.