2014 Sydney hostage crisis
After the siege began, a staged exclusion zone was established with thousands of people evacuated from nearby buildings, including from the floors above the café. The Sydney Opera House was evacuated after a suspicious package was found; however, reports were unconfirmed by police. The US Consulate General in Sydney, located in Martin Place, was also evacuated. Some Sydney schools were put in "white level lockout" due to the hostage situation, which meant that no school group was permitted to leave the school grounds.
Sydney Harbour defences
Sydney's defences were not expanded from their pre-Federation condition until the 1920s. During the 1920s a number of well-constructed fortifications were built to protect Sydney. Sydney's defences were further expanded following the outbreak of World War II and were considerably augmented once Japan entered the war. While Sydney's anti-submarine defences were not yet complete at the time of the attack on Sydney Harbour on the night of 31 May 1942, they were successful in sinking two of the three Japanese midget submarines which attempted to enter the Harbour; one submarine fired two torpedoes at a warship, both of which missed, one hitting another ship.