When raised across the entryway, it prevented ships from entering or leaving the inlet, serving as a simple but efficient form of defense.
After its construction in around 1000 CE, the chain was mainly used to keep enemy ships from entering the waterway, and attacking any of the undefended ports within Constantinople. It did so successfully for more than 400 years, with only rare cases of men circumventing it.
In 1511, the chain was raised by the Janissaries, in order to investigate the death of their Captain, Tarik Barleti, and prevent the one responsible from escaping by ship. However, the Assassin responsible, Ezio Auditore da Firenze, gained help from Yusuf Tazim and the other Ottoman Assassins to break through the defenses.
That day, Ezio destroyed the chain by bringing down one tower supporting it with a powerful explosive. He then proceeded to burn through the Ottoman fleet with Greek Fire, before escaping on a ship bound for Cappadocia.