Who (or what) was roosevelt referring to when he said, the hand that held the dagger has struck it into france's back?

On June 10,1940 US president Franklin D Roosevelt gave his famous speech "Stab in the Back" at University of Virginia.

On the speech He mentioned that the hand that held the dagger has struck into it's neighbor's back. Here he referred Italy and Mussolini as the hand which held dagger and France was the neighbor.

Because on June 10,1940 Italy declared war against France and Britain and joined to Germany on axis power. Mussolini said Italy was joining war against France and Britain as for keeping promise to Germany.

Roosevelt mentioned this incident for in his speech as the hand held dagger has struck into France's back.

Moreover, in this speech, He made a proclamation about removing America's neutral position in war and soon declared the Mediterranean see as a combat zone.

Explanation:

because its important to learn about other countries and how high tech they are compared to us. also its good to learn about other cultures and how ours differs and in common also we need to learn about companies that we still buy since they ship it here.