Four games into the season, Britain was at war with Nazi Germany and all official Scottish football competition was suspended for its duration.
In October 1939, in the absence of official competition, the clubs themselves wanted competitive football to continue in some form and arranged for two regional leagues of 16 teams each to be played, with Dumbarton playing in the Western Division – along with the likes of Celtic, Rangers etc.
Most of the First Division players were already contracted to play for their league opponents and it was no surprise that in this first season of the 'wartime' league, Dumbarton finished bottom (16th out of 16) with 18 points – 30 behind champions Rangers.
While the Dumbartonshire Cup competition had been discontinued some years earlier, during the weeks following the suspension of official competition and the start of the regional leagues, Dumbarton played Vale of Leven (a junior football side) for custody of the trophy, and the senior team duly won the day.
Dumbarton were knocked out at the semi-final stage by Falkirk, although the competition was never completed.