Hitler and Mussolini had a close relationship as fellow fascist dictators, and co-operated in Spain, but Mussolini refused several requests by Hitler to declare war on either the United Kingdom or the Soviet Union. Apparently he was tempted to join in as France was falling, but didn't for reasons that historians still are unclear about. Admittedly this is something of another Axis wank, or would Italy allying with Germany really made that big a difference? Either going in at the fall of France or joining in against the Soviet Union later could be PODs.