The medieval Byzantine Empire reached its height under the Macedonian emperors of the late 9th, 10th, and early 11th centuries, when it gained control over the Adriatic Sea, southern Italy, and all of the territory of the Tsar Samuil of Bulgaria. The cities of the empire expanded, and affluence spread across the provinces because of the new-found security. The population rose, and production increased, stimulating new demand while also helping to encourage trade.