and those that functioned as anti-aircraft artillery platforms were also called Flak towers. Some were over six stories high; several survive to this day because of the high cost of demolition. The in Berlin-Schöneberg has a post-war block of flats built over it. During the Cold War the shelter was in use as a NATO foodstore. In the guerrilla phase of the Irish Civil War (1922–1923), a network of blockhouses was constructed to protect the railways from guerrilla attacks. Blockhouses and coordinated road systems were used in the encirclement campaigns of Chiang Kai-shek against the Chinese Communist Party. See also Battery tower Blockhouse No. 1, New York City Block House (Delaware) British hardened field defences of World War II - Pillbox Caponier Casemate Chartaque Chardak Fort King George in Darien, Georgia Fort Pitt Block House in Point State Park in Pittsburgh Martello tower Ostrog (fortress) Sangar (fortification) Notes References External links Pillbox Study Group Royal Engineers Museum: Blockhouses during the Anglo-Boer War (1899–1902) Berlin Air-raid Shelters, Flak Towers and Bunkers Pillboxes British World War 2 Fortifications The Fortress Study Group Fortifications by type . Concrete buildings and structures Military science