The Siege of Luebeck, which took place in 1633 and 1634, was a turning point in the Ostend War. Luebeck, with Emperor Gustavus Adolphus in the city, was besieged and blockaded by land and naval forces of the League of Ostend. However, the city was not completely invested. After a successful attack by American scuba divers sank many Danish ships, the Danes were unwilling to send ships too far down the Trave. Also, the USE Air Force was occasionally able to attack the League forces, and it was even possible to fly people into and out of Luebeck with reasonable safety.