There is still a window for Ukraine and the West to achieve a victory, at first on the battlefield and then at the negotiating table, if the West increases the pace and volume of weapons deliveries to Kyiv and commits to stabilize Ukraine's economy. But these moves would come at an immense cost and could take many years. And so far, Europe and the United States seem hesitant to increase their support for Ukraine substantially. Unless Ukraine's allies in the West resist growing war fatigue, long-term factors appear more likely to favor Russia as the invasion grinds on....