I don’t know if Mussolini had doubts about Nazism, but he did rightfully have many doubts about Italy’s ability to wage war. Mussolini was an opportunist, and he was not about to stick his neck out in an extremely risky venture. Later in June, when it looks like a done deal, he will throw in his lot with Hitler.
Homer, I know you’ve been posting from “Rise and Fall of The Third Reich.” I’m too lazy to consult my copy, so refresh my memory if you will. Was this the conference where Il Duce made unrealistic demands to Germany to supply Italy with raw materials as necessary preconditions to Italy’s entry into the war? It was a deliberate demand for outrageous quantities of things like copper, iron ore and ferro-alloy metals. Mussolini knew full well that on some of the items, Hitler didn’t have any quantity at all. It was a bluff and he knew he wouldn’t be called on it.
I think that was part of Hitler's last minute machinations before invading Poland. On 25 August 1939 he had a back and forth with Mussolini, who was running hot and cold, as usual. Part of Il Duce's side of the conversation went as follows:
Our intervention can, nevertheless, take place at once if Germany delivers to us immediately the military supplies and the raw materials to resist the attack which the French and English would predominantly direct against us.
At our meetings the war was envisaged for 1942, and by that time I would have been ready on land, on sea and in the air, according to the plans which ad been concerted.