Other special event cards include particular key offensives, such as the Russian Brusilov or Kerensky Offensives, the German Verdun, Michael and Blücher Offensives or the Allied Gallipoli and Salonika landings. Other events include the sortie of the German High Seas Fleet (which may be defeated by play of the British "Grand Fleet" Card – statistically roughly a one in three chance of the Allies holding that card at the time) and German Unrestricted U-Boat Warfare, which prevents deployment of US or British reinforcements until defeated by play of the Allied "Convoy" Card.