Actually the tyrants can go on for a very long time lacking money to give to the peasants. Look at North Korea and Cuba for at least two examples. No, what ovethrows them is either lack of money to give to the security forces that keep El Jefe and his cronies on their blood-soaked thrones, or the US Army roling down the street and breaking down the doors to El Jefe’s palace. Since there is no chance of the latter in Iran’s case we must hope for the former as a result of the sanctions, but the experience with North Korea and Cuba shows that the tyrants can last a long time under such disadvantages, provided they allocate their straitened resources prudently to the guys with guns. Then they can let the peasants starve with impunity. Saddam did.