Introduction: The historical background -- Chronology -- Design and Development: The first fortifications ; The modernizations of the 1930s ; The weapons of the Mannerheim Line ; Standard elements of bunker design -- Field fortifications of the Mannerheim Line: Trenches ; Wooden bunkers ; Obstacles -- The principles of defence -- The living sites -- Operational history: The Inkila sector ; Karhula ; Summa village (Summankyla) ; Lahde ; Leipasuo ; Taasionlammet ; Suurniemi ; Muolaa ; Salmenkaita ; Kekkiniemi cannon fort ; Taipale and Patoniemi ; Aftermath -- The sites today -- Bibliography -- Appendix: The Mannerheim Line sectors