The Russian exclave of Kaliningrad is once again in the news, after a senior U.S. military commander on July 17 issued a stark warning to the Kremlin that NATO forces could take control of it "in a timeframe that is unheard of." The remarks from U.S. Army Europe and Africa commander General Chris Donahue are some of the strongest yet from a Western military official — a direct threat to the Kremlin about the consequences of further Russian aggression beyond Ukraine. They come amid ever-he...