The war with Germany
The German attack in the Balkans became even more imperative after the failure of the Italian spring attack in the Greek-Albanian front. The attack began in early March for the simple reason that Mussolini wished to rescue Italy's prestige alongside Germany by presenting the occupation of Greece as a joint operation of the Axis (and not solely of Germany).
In reality, the spring attack did not advance the Italian troops in the slightest towards the Albanian front and caused heavy human and material losses. On 18 March the Italian dictator, who had visited Albania in order to supervise the progress of the operation, returned to Italy angered and humiliated by the ineffectiveness of the Italian armed forces and especially of their leadership.
Due to that and the fact that Bulgaria and Yugoslavia joined the Reich, in March 1941, the German invasion appeared inevitable.