Last week, The New York Times broke the news that the aircraft the US used to attack a boat in the Caribbean last September, killing 11 people, had a paint job that made it look like a civilian plane. By using a plane with a nonmilitary appearance for a military operation, the Times wrote, the Trump administration may have committed a war crime called “perfidy.” Dictionary lookups for the word spiked the day the Times story was published, per Merriam-Webster. Perfidy — from the French perfidie via the Latin perfidia — means deceitfulness, treachery or a breach of faith or...