Once a vast fortification of 49 turrets, it ranked alongside Osaka and Nagoya as one of the country's greatest impregnable bastions.
It was such an impregnable bastion, no one has ever defeated it.
mnli hypothesis: It was such an impregnable bastion, no one has ever defeated it. premise: Once a vast fortification of 49 turrets, it ranked alongside Osaka and Nagoya as one of the country's greatest impregnable bastions.