quality:correction
The Great Chain of the Golden Horn

Fearing a possible naval attack along the shores of the Golden Horn, Emperor Constantine XI ordered that a defensive chain be placed at the mouth of the harbour. This chain, which floated on logs, was strong enough to prevent any Turkish ship from entering the harbour. This device was one of two that gave the Byzantines some hope of extending the siege until the possible arrival of foreign help. This strategy was used because in 1204, the armies of the Fourth Crusade successfully circumvented Constantinople's land defences by breaching the Golden Horn Wall, which faces the Horn. Another strategy employed by the Byzantines was the repair and fortification of the Land Wall (Theodosian Walls). Emperor Constantine deemed it necessary to ensure that the Blachernae district's wall was the most fortified because that section of the wall protruded northwards. The land fortifications consisted of a 60 ft (18 m) wide moat fronting inner and outer crenellated walls studded with towers every 45–55 metres.