Short answers, pulled from the story.
The Greco-Italian War began on the 28th of October 1940 after Italy issued an ultimatum demanding free passage for troops. Prime Minister Ioannis Metaxas rejected this demand with the words then it is war which initiated hostilities.
Benito Mussolini and Navy chief Domenico Cavagnari ordered the Italian submarine Delfino to sink the Greek light cruiser Elli. This attack occurred on the 15th of August 1940 during the Dormition of the Theotokos holiday in Tinos harbour.
Italian units reached their deepest point at Margariti but could not advance further than the Kalamas river by the 13th of November 1940. Mountainous terrain and muddy conditions hindered movement while poor roads delayed advances significantly along the border.
The city of Korçë fell to the 9th Division on the 22nd of November 1940 after Italians retreated toward the Devoll valley. The TSDM captured the entire Korçë plateau by the 27th of November suffering six hundred dead and two thousand three hundred wounded.
German troops invaded northern Greece under Operation Marita on the 6th of April 1941 altering the course of the campaign. Hitler decided that increased British intervention represented a threat to Germany's rear while build-up accelerated after Bulgaria joined the Axis on the 1st of March 1941.