The victorious German Blitzkrieg assault on Holland, Belgium and Northern France placed Anglo-French relations under huge strain. The Vichy surrender raised real British fears that the Germans would force the French Fleet, the fourth largest in the world, to turn against their former ally, while in fact their orders were to scuttle in the event of the Germans attempting to seize them.

At War With Our Ally examines the background to the fall of France and its consequences, most particularly the way the French Navy was dealt with. It studies the confused situation that the chaos of devastating defeat created including the rise of a relatively junior French general, Charles de Gaulle who was smuggled out of France by the RAF on the night of 16/17 June.

Elsewhere French ships were boarded and seized by the British and at Oran, their Fleet was bombarded by the Royal Navy. There were numerous other incidents with French aircraft bombing Gibraltar.