In the aftermath of the staggering victory at Adrianople, Constantine's army marched on Byzantium. When he crested the final hill and saw the city for the first time, not as a set of lines on a surveyor's map but as a living, breathing fortress, he felt a moment of cold, professional admiration. His secret surveys had not done it justice. The city sat on a triangular peninsula of rock, a natural fortress protected on two sides by the deep blue waters of the Propontis and the sheltered inlet of the Golden Horn. On its landward side, it was defended by a formidable wall, studded with towers. As long as Licinius controlled the sea, Byzantium could be resupplied and reinforced indefinitely.
"He has fled to the strongest fortress in his domain," Metellus observed grimly, riding alongside him. "A direct assault is impossible. His fleet is his shield wall now."
