The pillboxes of Britain and Ireland are among the most important military structures employed in the history of the defence of these islands. This work presents the first thorough study and classification of pillboxes and related structures, including selection posts, Seagull and concrete trenches, gun-houses and turrets, battle headquarters and spigot-mortar emplacements. The author traces the use of small, free-standing defence structures from ancient times to the present, placing the pillbox within a historical continuum and identifying its course of development. The work also presents a typology of British and Irish pillboxes through a catalogue of known types and individual examples, and examines their tactical employment in the landscape. Mike Osbourne has been involved in the recording of defence structures for over 30 years and was co-ordinator of the Defence of Britain Project in the eastern counties. He is also the author of Defending Britain: Twentieth-Century Military Structures in the Landscape, also published by The History Press.