There is an old, half tired joke at the State Department that the truth, like an American passport, must clear three layers of review before it is allowed to leave the building. But for diplomats on the front lines of the information wars, the joke has never been funny. A young officer in some faraway embassy might watch a deliberately fake video go viral on local social media—a fabricated atrocity, a doctored politician’s speech, a Russian or Chinese narrative designed to poison an alliance—and then realize that the only people authorized to respond are sitting in Washington, in a specialized…

It started with a clip that felt wrong. This September, I saw a post claiming that Hillary Clinton, the former U.S. senator and secretary of state, had urged Taiwan to surrender. It had tens of thousands of likes and thousands of shares, and it was moving fast through Taiwan’s Chinese-language social media. Something about it didn’t sit right, so I checked. The truth was revealing. On September 10, Clinton had appeared on “Morning Joe” for a September 11 anniversary special to discuss President Donald Trump’s national security strategy. She was talking about Iran, and about how China and Russia were…