There has long been a worry that Russian escalation or miscalculation might see the Ukraine war widen into a broader European one. But what if it’s Kyiv, not Moscow, that starts this process? The flashpoint is Belarus. Minsk’s dictatorial leader, Alexander Lukashenko, is beholden to Vladimir Putin, but not a helpless vassal. On the one hand, he has refused to join Putin’s war directly, saying that he won’t allow Belarusians to become ‘mincemeat.’ On the other, he has been willing to let Russian troops use facilities in his country, and fly drones and missiles through his airspace. There is growing...