Donald Trump promised to “Drain the Swamp,” by which he originally meant lobbyists. When he got in, he found an entirely different Swamp—a Deep State that had grown, layer upon layer, within the government. But he wasn’t the first to encounter entrenched Swamp opposition. Abraham Lincoln had to battle the “Slave Power Conspiracy”; Grover Cleveland was the most successful of three presidents to fight the spoils Swamp. Theodore Roosevelt found a new iteration of the Swamp awaiting him: Trusts. After World War II, John F. Kennedy discovered that he had little control over the Central Intelligence Agency, and even found he needed the CIA for his own purposes. Despite promising to shrink the bureaucracy Swamp, Ronald Reagan found himself helpless to even make a dent in it. And Trump soon learned that the Deep State could ensure no one ever brought any of its own to justice. Dragonslayers explains why these Swamps exist, and why they were—and remain—so hard to defeat.