Yekatit 12 (Amharic: የካቲት ፲፪, romanized: Yekatīt 12) is a date in the Ge'ez calendar which refers to the massacre and imprisonment of Ethiopians by the Italian occupation forces following an attempted assassination of Marshal Rodolfo Graziani, Marquis of Negele, Viceroy of Italian East Africa, on February 19, 1937. Graziani had led the Italian forces to victory over the Ethiopians in the Second Italian invasion of Ethiopia and was supreme governor of Italian East Africa. This has been described as the worst massacre in Ethiopian history.Estimates vary on the number of people killed in the three days that followed the attempt on Graziani's life. Ethiopian sources estimated that 30,000 people were killed by the Italians, while Italian sources claimed that only a few hundred were killed. A 2017 history of the massacre estimated that 19,200 people were killed, 20 percent of the population of Addis Ababa. Over the following week, numerous Ethiopians suspected of opposing Italian rule were rounded up and executed, including members of the Black Lions and other members of the aristocracy. Emperor Haile Selassie had sent 125 men abroad to receive college education, but most of them were killed. Many more were imprisoned, even collaborators such as Ras Gebre Haywot, the son of Ras Mikael of Wollo, Brehane Markos, and Ayale Gebre, who had helped the Italians identify the two men who made the attempt on Graziani's life.