The long prelude to war in 1939

Where should a reader look for the background to the outbreak of the Second World War?

Look at the months of tension, rearmament, stockpiling, and planning before September 1939 rather than treating the outbreak as sudden.

The approach to war was visible well before 1 September 1939. The Royal Navy was pushing to complete ships, while supplies moved around the world to support stockpiling before the convoy system was fully in place. Planning and tension had therefore shaped naval activity for months before open fighting began. In this reading, appeasement was partly an attempt to buy time for rearmament under intense political uncertainty.