At this point, the United States has sent more than $17 billion in cash and military aid to Ukraine for that nation’s fight against the Russians. The United States has been far and away the largest, most generous patron of Ukraine’s government of any of the allies who are supporting this effort. But this has dragged on for quite a while now and it is long past time to begin seriously discussing the obvious question. How long are we supposed to keep this up? In fairly short order, the money we’ve sent to Ukraine will more than double the annual...