The Ohi day ultimatum, which was presented to Metaxas by the Italian ambassador in Greece, Emanuele Grazzi, on October 28, 1940, at dawn (04:00 am), after a party in the German embassy in Athens, demanded that Greece allow Axis forces to enter Greek territory and occupy certain unspecified “strategic locations” or otherwise face war. It was allegedly answered with a single laconic word: όχι or no. In response to Metaxas’s refusal, Italian troops stationed in Albania, then an Italian protectorate, attacked the Greek border at 05:30 am. Metaxas’s reply marked the beginning of Greece’s participation in World War II
On the morning of October 28 the Greek population took to the streets, irrespective of political affiliation, shouting ‘ohi’. From 1942, it was celebrated as Ohi Day. During the war, October 28 was commemorated yearly by Greek communities around the world and in Greece and Cyprus, and after World War II it became a public holiday in Greece and Cyprus. The events of 1940 are commemorated every year with military and student parades. On every anniversary, most public buildings and residences are decorated with Greek flags.