You might've missed a line that was tucked away in Donald Trump's recent speech. He called on the admirals and generals to be ready to fight “the enemy from within” in American cities. Authoritarians like Lenin, Stalin, and even Hitler have used variants of this phrase to delegitimize and demonize their opponents and to justify horrific acts of repression, from smothering debate to imprisoning and executing rivals and critics. That’s Trump’s line—and it’s a dangerous escalation.