In 1551, an Ottoman force briefly attacked Malta, and then sacked Gozo and captured Tripoli, and as a result, the Order set up a commission to improve the island's fortifications. In 1552, the Aragonese watchtower was demolished and Fort Saint Elmo was built in its place. The fort played a significant role in the Great Siege of Malta of 1565. It eventually fell after a month of fierce fighting (in which the Ottoman general Dragut was killed). The knights held out in Birgu and Senglea until a relief force arrived, and the siege was lifted.