Mussolini surprised everyone with a move against Greece; his ally, Hitler, was caught off guard, especially since the Duce had led Hitler to believe he had no such intention. Even Mussolini’s own chief of army staff found out about the invasion only after the fact!
Despite being warned of an invasion of Greece by his own generals, despite the lack of preparedness on the part of his military, despite that it would mean getting bogged down in a mountainous country during the rainy season against an army willing to fight tooth and nail to defend its autonomy, Mussolini moved ahead out of sheer hubris, convinced he could defeat the inferior Greeks in a matter of days. He also knew a secret, that millions of lire had been put aside to bribe Greek politicians and generals not to resist the Italian invasion. Whether the money ever made it past the Italian fascist agents delegated with the responsibility is unclear; if it did, it clearly made no difference whatsoever—the Greeks succeeded in pushing the Italian invaders back into Albania after just one week. The Axis power spent the next three months fighting for its life in a defensive battle. To make matters worse, virtually half the Italian fleet at Taranto had been crippled by a British carrier-based attack.
At their meeting in Obersalzberg, Hitler excoriated Ciano for opening an opportunity for the British to enter Greece and establish an airbase in Athens, putting the Brits within striking distance of valuable oil reserves in Romania, which Hitler relied upon for his war machine. It also meant that Hitler would have to divert forces from North Africa, a high strategic priority, to Greece in order to bail Mussolini out. Hitler considered leaving the Italians to fight their own way out of this debacle—possibly even making peace with the Greeks as a way of forestalling an Allied intervention. But Germany would eventually invade, in April 1941, adding Greece to its list of conquests.