The French air ministry issued a specification for a fighter that could also be used during the day or night in 1934 / October 1934.
Work on the designs started in 1935.
The Breguet 690 prototype was 2,200 lb / 1,000 kg heavier than the specification and was initially rejected. However, it's rival was slower so the Breguet 690 was selected and developed into the Breguet 691.
The engines could be removed and overhauled in 90 minutes.