During the
Second Italo-Ethiopian War,
Dejazmach Mengesha led a contingent of warriors from Gojjam at the
Battle of Shire, which was virtually annihilated. Following this, he retreated back to his homeland of northern Gojjam, where he began to organize a resistance against the Italian occupation. Mengesha mobilized an army of around 5,000 brigands and harassed Italian units in
Gojjam from mid to late 1937. Following the defeat of
Hailu Kebede's revolt in
Lasta in September 1937, the Italians attempted to pacify the
Amhara Governorate by launching an offensive against the guerrillas in
Gojjam. The new offensive immediately began with a disaster when on 7 December 1937, the VI Arab-Somali battalion led by
Pietro Grosso was attacked and completely destroyed by the guerrillas of Mengesha Jembere. Despite this setback, the new viceroy,
Prince Amedeo, Duke of Aosta, was eager to crush the guerrillas before the rainy season began. The new cycle of counterinsurgency operations began on 19 January 1938 in Gojjam, which was attacked from the north and south by three separate columns while other forces blocked the fords on the
Blue Nile to prevent the guerrillas from escaping. From January to March, there were fierce battles in Gojjam between the Italians and the guerrillas of Mengesha and
Belay Zeleke, with heavy losses for both sides. The Italians lost 350 dead and 1,200 wounded, the majority of whom were
askaris but also included Italian officers such as
Giovanni Thun Hohenstein, and . Despite these heavy losses, these clashes ended in March 1938 with the dispersal of Mengesha, who lost nearly half his men. Mengesha managed to avoid death or capture during the roundups despite a serious lack of food and ammunition. However, he seemed relatively optimistic, and in August 1938, he wrote a letter to
Haile Selassie, pledging his allegiance to the Emperor and vowing to expel the Italians from Ethiopia. From the summer of 1938 to the spring of 1940, Mengesha's activities caused great frustration to the Italian garrison in
Debre Markos, and he was considered to be one of the most active and dangerous guerrilla leaders in
Italian East Africa. After the outbreak of the
Second World War, Mengesha established contact with the British forces in
Sudan, who gave him a consistent supply of weapons and ammunition. During the
East African campaign, Mengesha's guerrillas accompanied the
Gideon Force during their advance into
Italian East Africa, seizing the town of
Dangila before the arrival of British forces and helping them take
Debre Markos on 6 April 1941. ==Later career==