STOCKHOLM, July 3 -- Two drones crossed into the grounds of Russia's embassy in Stockholm on Thursday. The first, a quadrocopter, deployed a container of red paint across the compound. The second landed near the chancery building carrying what Russian diplomats described as a simulated improvised explosive device. Nobody was hurt. The question of who sent them, as after fifteen previous incidents at the same address, remained unanswered.

The Russian Embassy in Sweden said it had been "once again attacked by unmanned aerial vehicles." The phrase "once again" does considerable work in a sentence that described a quadrocopter dropping paint and a second drone falling near the building with a device designed to resemble a bomb. The embassy c...