The Official History of New Zealand in the Second World War 1939–45 is a 48-volume series published by the War History Branch (and its successors) of the Department of Internal Affairs which covered New Zealand involvement in the Second World War. The series was published during the period 1949 to 1986. A collection of booklets entitled Episodes and Studies were also published between 1948 and 1954. The Official History of New Zealand in the Second World War 1939–45 was the largest publication project undertaken in New Zealand.