Benito Mussolini launched the Second Italo-Ethiopian War on 3 October 1935, invading from the Italian colony of Eritrea without a declaration of war. The opening phase under General Emilio De Bono moved slowly, and Mussolini replaced him in December with Marshal Pietro Badoglio. By early January 1936, Badoglio had five army corps facing the Ethiopian forces along the northern front. The Ethiopians were in three groupings: Ras Kassa Haile Darge and Ras Seyoum Mangasha in the Tembien with about 70,000 men; Ras Imru Haile Selassie in Shire province with about 40,000; and Ras Mulugeta Yeggazu, with his 80,000 soldiers, dug in on the flat-topped mountain of Amba Aradam in Enderta Province. The mountain had two features the Italians named with offhand colonialism: a jagged ridge they called The Herringbone, and a peak on the extreme right they called The Priest's Hat.

The forces were roughly equal in number - the Italians attacking with comparable manpower. The material difference was staggering. Italian fascist forces at Amba Aradam commanded over 5,000 machine guns, 280 pieces of artillery, and 170 aircraft of the Regia Aeronautica, some of which were routinely equipped to spray mustard gas on Ethiopian troops and the civilians of the villages around them. Against that Ras Mulugeta had 400 machine guns, 18 old field pieces of medium caliber, a few anti-aircraft guns, and not a single airplane. The one advantage he did have was the steep slopes of Amba Aradam itself - a natural fortress the Italians would have to climb under fire. Mussolini pushed Badoglio for an early offensive. The Italian press was hungry for victories. Ethiopian civilians fled to caves. Haile Selassie, in Addis Ababa, waited for news.

At 8:00 AM on 10 February 1936, Badoglio launched his attack. Royal Italian Army troops and fascist Blackshirts led the advance, with Eritrean askari conscripts held in reserve. The I and III Army Corps advanced across the Kalamino Plain, reaching the May Gabat River by nightfall. Badoglio directed the battle from a headquarters that doubled as the artillery observation post; every five minutes, scout planes of the Regia Aeronautica circled the front and radioed fresh target coordinates down to the gunners. On 11 February, the 4th Blackshirt Division and the 5th Alpine Division began moving around the west side of the mountain while the III Army Corps circled east. Ras Mulugeta recognized the encirclement too late. Under cover of darkness and heavy cloud on the night of 14-15 February, the Italians closed the pincers. When the cloud lifted on the morning of the 15th, the Ethiopians tried to break out down the western slopes toward Addi Kolo. The Italian air force and artillery stopped the breakout cold.

Ras Mulugeta's son, Tadessa Mulugeta, served on the mountain as asmach, a traditional Ethiopian military rank. He was killed in an action against Galla tribal forces during the battle, and his body was mutilated. When news reached his father, Ras Mulugeta turned back alone to recover his son's remains. A strafing run by an Italian aircraft killed him on the way. With their commander dead and their formations broken by air attack, the surviving Ethiopian soldiers on Amba Aradam disintegrated. The mountain fell. Badoglio now turned to the Ethiopian center, fighting the Second Battle of Tembien against Ras Kassa and Ras Seyoum. The Ethiopian forces at Amba Aradam had lasted five days against mustard gas, modern artillery, and saturation air power. In the Italian press, the victory became Ambaradan - a word that entered Italian slang meaning a huge confused mess, still in use today.

The Italian use of mustard gas in Ethiopia was not a secret. The Ethiopian government filed formal complaints with the League of Nations during and after the war, citing specific attacks on soldiers and civilians. Italian veterans later described spraying yperite from low-flying aircraft onto concentrations of Ethiopian troops. The chemical attacks continued through the campaign and into the guerrilla war that followed Italy's 1936 occupation. The League of Nations responded to all of it with sanctions that Britain and France refused to enforce, and Mussolini's march on Addis Ababa continued. Emperor Haile Selassie, forced into exile, addressed the League in Geneva in June 1936 and warned that the same powers refusing to stop Italian poison gas in Africa would soon face worse. The Italian occupation of Ethiopia lasted until 1941, when British Empire forces and Ethiopian Arbegnoch - Patriot - guerrillas drove the fascists out. The Ethiopian dead at Amba Aradam were never precisely counted. They had fought a losing fight against weapons the Italians knew the Ethiopians could not answer.