Ukraine has a future. And the West has a crucial role to play in what that future looks like. Recently, I joined a group of Western security experts on a trip to Ukraine organized by the Warsaw-based Polish Institute of International Affairs. We met with the Ukrainian president. We visited Bucha, the high-water mark of the Russian incursion toward Kyiv, where the invaders massacred hundreds of civilians. We saw a lot in a few days — but anyone who spends a few days in a war zone and then claims to know exactly what is going on is talking nonsense. Nonetheless, the state of what is now a very long war is clear, as are America’s obligations and opportunities. For starters, it is in the interest of the West, particularly the United States, to see a free and independent Ukraine. Russian appetites won’t stop with Ukraine. Vladimir Putin’s grand vision is to reabsorb the post-Soviet states, establish dictatorial control over central Europe, and see NATO dissolve and all U.S. military presence removed from Europe. These goals are a death sentence for the trans-Atlantic community. More sinister, they are fully supported by China, which would benefit most from a weakened, divided, and distracted Europe. Supporting Ukraine to thwart Putin’s and Chinese leader Xi Jinping’s ambitions makes all the sense in the world. Further, there’s the matter of basic self-interest. The day after we left Ukraine, another...