At the beginning of Italian participation in the First World War, he was a lieutenant colonel (tenente colonnello); he rose to the rank of major general following his handling of the capture of Monte Sabotino in May 1916 and by the late months of 1917, by now already a lieutenant general, was named as vice-chief of staff (sottocapo di stato maggiore) despite being one of those mainly responsible for the disaster during the Battle of Caporetto on 24 October 1917.

[3] In the years after the First World War, in which he held several high posts in the Regio Esercito, Badoglio exerted a constant effort in modifying official documents in order to hide his role in the defeat.

During his governorship, he played a vital part (with Rodolfo Graziani, deputy governor of Cyrenaica) in defeating the Libyan Resistance by waging a near-genocidal campaign.

On 20 June 1930, Badoglio wrote to Graziani: "As for overall strategy, it is necessary to create a significant and clear separation between the controlled population and the rebel formations.

"[6] By 1931, well over half of the population of Cyrenaica were confined to 15 concentration camps where many died as a result of overcrowding (and lack of water, food and medicine) while Badoglio's air force used chemical weapons against the Bedouin rebels in the desert.

Badoglio asked for and was given permission to use chemical weapons, using the torture and murder of downed Italian pilot Tito Minniti during the Ethiopian "Christmas Offensive" as a pretext for doing so.

British historian Sir Ian Kershaw wrote the "barbarous initiatives in the conduct of the war in Ethiopia" came as a rule from the military elite rather than from Mussolini himself.

On this occasion, Badoglio was appointed the first viceroy and governor general of Ethiopia and ennobled with the victory title of Duke of Addis Abeba ad personam.

[8] Badoglio was chief of staff from 1925 to 1940, and had the final say on the entire structure of the Armed Forces, including doctrine, selection of officers, and armaments, influencing the whole military environment.

[12] On 15 July 1943, in a secret meeting Victor Emmanuel told Badoglio that he would soon be sworn in as Italy's new prime minister and the king wanted no "ghosts" (i.e. liberal politicians from the pre-fascist era) in his cabinet.

On 3 September 1943, General Giuseppe Castellano signed the Italian armistice with the Allies in Cassibile on behalf of Badoglio, who was named Prime Minister of Italy.

In the early hours of the following day, 9 September 1943, Badoglio, King Victor Emmanuel, some military ministers, and the chief of the general staff escaped to Pescara and Brindisi seeking Allied protection.