As a practical matter, any modern military offensive launched without air cover is a suicide mission. Ukraine no longer has much of an air force, even with the addition of perhaps a dozen or so old MIG-29s acquired from NATO countries. Some of those are not flyable and others are being disassembled and used for parts. Ukraine’s operational fighter aircraft have to fly against more advanced Russian fighters including the formidable Su-35, and survive in combat against mobile Russian air defenses. Whatever Ukraine has, its air force cannot be expected to last more than a few days in a major...