Ivan Asen II of Bulgaria
Meanwhile, the Bulgarian Empire threatened Byzantine control of Northern Greece and the Aegean coast to the south. Under Presian I and his successor Boris I, the Bulgarian Empire managed to obtain a small portion of the northern Aegean coast. Simeon I of Bulgaria led Bulgaria to its greatest territorial expansion, and managed to conqueror much of the northern and western coasts of the Aegean. The Byzantines later regained control. The Second Bulgarian Empire achieved similar success along, again, the northern and western coasts, under Ivan Asen II of Bulgaria.