The Second Italo-Ethiopian War, also referred to as the Second Italo-Abyssinian War, was a war of aggression waged by Italy against Ethiopia, which lasted from October 1935 to May 1936. In Ethiopia it is often referred to simply as the Italian Invasion (Amharic: ጣልያን ወረራ, romanized: Ṭalyan warära), and in Italy as the Ethiopian War (Italian: Guerra d'Etiopia). The war is regarded as the largest colonial campaign in history.
On 3 October 1935, two hundred thousand soldiers of the Regio Esercito (Royal Army) commanded by Marshal Emilio De Bono attacked from Italian Eritrea without prior declaration of war. At the same time a smaller force under General Rodolfo Graziani attacked from Italian Somalia. On 6 October, Adwa was conquered, a symbolic place for the Italian army as it was the site of their defeat at the Battle of Adwa during the First Italo-Ethiopian War. On 15 October, Italian troops seized the town of Aksum, and its famous obelisk was torn from its site and sent to Rome to be placed symbolically in front of the building of the Ministry of Colonies.
Exasperated by De Bono's slow and cautious progress, Benito Mussolini replaced him with General Pietro Badoglio. Ethiopian forces launched a counterattack in December 1935 that achieved some gains and temporarily halted the Italian advance. Frustrated, Mussolini authorized the use of mustard gas, with the Regia Aeronautica (Royal Air Force) dropping 330 tons over the next four months, violating the 1925 Geneva Protocol. The Italians resumed the offensive in early February, decisively defeating the Ethiopian army at Amba Aradam, Tembien, and Shire. On 31 March 1936, the Italians won a decisive victory at the Battle of Maychew, which nullified any possible organized Ethiopian resistance. Emperor Haile Selassie was forced to flee into exile on 2 May, and Badoglio's forces arrived in the capital Addis Ababa on 5 May. Mussolini then announced the annexation of Ethiopia on 9 May and the colony of Italian East Africa was formed. Hostilities did not cease with the end of conventional war operations and Ethiopian resistance to Italian rule would continue until the country was liberated in 1941.
Overall, the war in Ethiopia was a major military success for the fascist regime in Italy, achieved relatively quickly and with considerable propaganda value. However, it also placed a significant strain on an already seriously unbalanced budget, weakening Italy's long-term economic position. The Italian aggression against Ethiopia had significant diplomatic consequences, leading to the end of the Stresa Front and Italy's rapprochement with Nazi Germany. Simultaneously, the inability of the League of Nations to prevent the invasion discredited it internationally on the eve of the Second World War.
Italian troops used mustard gas in aerial bombardments (in violation of the Geneva Protocol and Geneva Conventions) against combatants and civilians in an attempt to suppress Ethiopian resistance. Deliberate Italian attacks against ambulances and hospitals of the Red Cross were reported. By all estimates, hundreds of thousands of Ethiopian civilians died as a result of the Italian invasion, which have been described by some historians as constituting genocide. Crimes by Ethiopian troops included the use of dumdum bullets (in violation of the Hague Conventions), the killing of civilian workmen (including during the Gondrand massacre) and the mutilation of captured Eritrean Ascari and Italians (often with castration).
The Kingdom of Italy began its attempts to establish colonies in the Horn of Africa in the 1880s. The first phase of the colonial expansion concluded with the disastrous First Italo-Ethiopian War and the defeat of the Italian forces in the Battle of Adwa on 1 March 1896, inflicted by the Ethiopian Army of Negus Menelik II. In the following years, Italy abandoned its expansionist plans in the area and limited itself to administering the small possessions that it retained in the area: the colony of Italian Eritrea and the protectorate (later colony) of Italian Somaliland. For the next few decades, Italian-Ethiopian economic and diplomatic relations remained relatively stable.
On 14 December 1925, Italy's fascist government signed a secret pact with Britain aimed at reinforcing Italian dominance in the region. London recognised that the area was of Italian interest and agreed to the Italian request to build a railway connecting Somalia and Eritrea. Although the signatories had wished to maintain the secrecy of the agreement, the plan soon leaked and caused indignation by the French and Ethiopian governments. The latter denounced it as a betrayal of a fellow member country of the League of Nations.
As fascist rule in Italy became increasingly dictatorial, its colonial governors in the Horn of Africa began pushing outward the margins of their imperial foothold. The governor of Italian Eritrea, Jacopo Gasparini, focused on attempting to win over the leaders of the Tigrinya people against Ethiopia. The governor of Italian Somaliland, Cesare Maria de Vecchi, began a policy of repression that led to the absorption of the fertile Jubaland and the annexation of various Somali protectorates during the Campaign of the Sultanates.
The Italo-Ethiopian Treaty of 1928 stated that the border between Italian Somaliland and Ethiopia was 21 leagues parallel to the Benadir coast (approximately 118.3 kilometres [73.5 miles]). In 1930, Italy built a fort at the Walwal oasis (also Welwel, Italian: Ual-Ual) in the Ogaden and garrisoned it with Somali dubats (irregular frontier troops commanded by Italian officers). The fort at Walwal was well beyond the 21-league limit and inside Ethiopian territory. On 23 November 1934, an Anglo–Ethiopian boundary commission studying grazing grounds to find a definitive border between British Somaliland and Ethiopia arrived at Walwal.
The party contained Ethiopian and British technicians and an escort of around 600 Ethiopian soldiers. Both sides knew that the Italians had installed a military post at Walwal and were not surprised to see an Italian flag at the wells. The Ethiopian government had notified the Italian authorities in Italian Somaliland that the commission was active in the Ogaden and requested the Italians to co-operate. When the British commissioner Lieutenant-Colonel Esmond Clifford, asked the Italians for permission to camp nearby, the Italian commander, Captain Roberto Cimmaruta, rebuffed the request.
Fitawrari Shiferra, the commander of the Ethiopian escort, took no notice of the 150 Italian and Somali troops and made camp. To avoid being caught in an Italian–Ethiopian incident, Clifford withdrew the British contingent to Ado, about 20 mi (32 km) to the north-east, and Italian aircraft began to fly over Walwal. The Ethiopian commissioners retired with the British, but the escort remained. For ten days both sides exchanged menaces, sometimes no more than 2 m apart. Reinforcements increased the Ethiopian contingent to about 1,500 men and the Italians to about 500, and on 5 December 1934, shots were fired. The Italians were supported by an armoured car and bomber aircraft. The bombs missed, but machine gunfire from the car caused about 110 Ethiopian casualties. 30 to 50 Italians and Somalis were killed. The incident led to the Abyssinia Crisis at the League of Nations. On 4 September 1935, the League of Nations exonerated both parties for the incident.
Britain and France, preferring Italy as an ally against Germany, did not take strong steps to discourage an Italian military buildup on the borders of Italian Eritrea and Italian Somaliland. Because of the German question, Mussolini needed to deter Hitler from annexing Austria while much of the Italian Army was being deployed to the Horn of Africa, which led him to draw closer to France to provide the necessary deterrent. King Victor Emmanuel III shared the traditional Italian respect for British sea power and insisted to Mussolini that Italy must not antagonise Britain before he assented to the war. In that regard, British diplomacy in the first half of 1935 greatly assisted Mussolini's efforts to win Victor Emmanuel's support for the invasion.