“When you play the game of thrones, you win or you die. There is no middle ground.” That’s a line from “Game of Thrones,” the new HBO television series that is conquering American popular culture.

But it could just as easily refer to the no-holds-barred battles we are watching in Libya and Syria. What is hardest to grasp is how these regimes are both strong and brittle. Their rulers are ruthless dictators prepared to do whatever it takes to stay in power — and for decades that can work. Until, suddenly, it does not.

We are not very good at understanding the win-or-die dynamic of these sorts of political systems: Not so long ago, everyone from the U.S. State Department, to Harvard, to the London School of Economics, to Vogue magazine, to blue-chip Wall Street money managers treated the Assads and the Qaddafis like rulers capable of gradual liberalization and even democratization.

Part of the problem is that the Cold War habit of mind, with its division of the world into two rival, ideologically cohesive camps, dies hard. Its legacy today is our tendency to look for a new, black-and-white division, this time into democracies and dictatorships. (Remember the axis of evil.) But modern dictatorships come in many different varieties. The ones that are collapsing in the Middle East are examples of what political scientists call “sultanistic” dictatorships.

According to Jack A. Goldstone, a professor at the School of Public Policy at George Mason University in Virginia, the defining characteristic of a sultanistic regime is that it has no purpose apart from maintaining the leader’s personal authority. “A sultanistic regime is one in which the leader of a country has managed to gain control of all the levers of state power,” Mr. Goldstone said. “No one has any secure rights, and the leader rules with absolute authority.”