The Kingdom of Italy was governed by the National Fascist Party from 1922 to 1943 with Benito Mussolini as prime minister. The Italian Fascists imposed authoritarian rule and crushed political and intellectual opposition, while promoting economic modernization, traditional social values and a rapprochement with the Roman Catholic Church. According to Payne (1996), "[the] Fascist government passed through several relatively distinct phases". The first phase (19221925) was nominally a continuation of the parliamentary system, albeit with a "legally-organized executive dictatorship". The second phase (19251929) was "the construction of the Fascist dictatorship proper". The third phase (19291934) was with less interventionism in foreign policy. The fourth phase (19351940) was characterized by an aggressive foreign policy: the Second Italo-Ethiopian War, which was launched from Eritrea and Somaliland; confrontations with the League of Nations, leading to sanctions; growing economic autarky; invasion of Albania; and the signing of the Pact of Steel. The fifth phase (19401943) was World War II itself which ended in military defeat, while the sixth and final phase (19431945) was the rump Sal Government under German control.Italy was a leading member of the Axis powers in World War II, battling on several fronts with initial success. However, after the German-Italian defeat in Africa, the successes of the Soviet Union on the Eastern Front, and the subsequent Allied landings in Sicily, King Victor Emmanuel III overthrew and arrested Mussolini, and the Fascist Party in areas (south of Rome) controlled by the Allied invaders was shut down. The new government signed an armistice with the Allies in September 1943. Nazi Germany, with Fascists' help, seized control of the northern half of Italy and freed Mussolini, setting up the Italian Social Republic, a collaborationist puppet state still led by Mussolini and his Fascist loyalists. Italian resistance to Nazi German occupation and Italian Fascist collaborators manifested in the four days of Naples, while the Allies organized some Italian troops in the south into the Italian Co-belligerent Army, which fought alongside the Allies for the rest of the war. A smaller number of Italian troops continued to fight alongside the Germans in the National Republican Army. From this point on, the country descended in civil war, and a large Italian resistance movement fought a guerrilla war against the German and RSI forces. Mussolini was captured and killed on 28 April 1945 by the Italian resistance, and hostilities ended the next day.

Shortly after the war, civil discontent led to the 1946 institutional referendum on whether Italy would remain a monarchy or become a republic. Italians decided to abandon the monarchy and form the Italian Republic, the present-day Italian state.

The League of Nations (French: Société des Nations [sɔsjete de nɑsjɔ̃]) was the first worldwide intergovernmental organisation whose principal mission was to maintain world peace. It was founded on 10 January 1920 by the Paris Peace Conference that ended the First World War. The main organization ceased operations on 20 April 1946 but many of its components were relocated into the new United Nations.

The League's primary goals were stated in its Covenant. They included preventing wars through collective security and disarmament and settling international disputes through negotiation and arbitration. Its other concerns included labour conditions, just treatment of native inhabitants, human and drug trafficking, the arms trade, global health, prisoners of war, and protection of minorities in Europe. The Covenant of the League of Nations was signed on 28 June 1919 as Part I of the Treaty of Versailles, and it became effective together with the rest of the Treaty on 10 January 1920. The first meeting of the Council of the League took place on 16 January 1920, and the first meeting of Assembly of the League took place on 15 November 1920. In 1919 U.S. president Woodrow Wilson won the Nobel Peace Prize for his role as the leading architect of the League.

The diplomatic philosophy behind the League represented a fundamental shift from the preceding hundred years. The League lacked its own armed force and depended on the victorious First World War Allies (Britain, France, Italy and Japan were the permanent members of the Executive Council) to enforce its resolutions, keep to its economic sanctions, or provide an army when needed. The Great Powers were often reluctant to do so. Sanctions could hurt League members, so they were reluctant to comply with them. During the Second Italo-Ethiopian War, when the League accused Italian soldiers of targeting International Red Cross and Red Crescent Movement medical tents, Benito Mussolini responded that "the League is very well when sparrows shout, but no good at all when eagles fall out."At its greatest extent from 28 September 1934 to 23 February 1935, it had 58 members. After some notable successes and some early failures in the 1920s, the League ultimately proved incapable of preventing aggression by the Axis powers in the 1930s. The credibility of the organization was weakened by the fact that the United States never joined the League and the Soviet Union joined late and was soon expelled after invading Finland. Germany withdrew from the League, as did Japan, Italy, Spain and others. The onset of the Second World War in 1939 showed that the League had failed its primary purpose; it was inactive until its abolition. The League lasted for 26 years; the United Nations (UN) replaced it in 1946 and inherited several agencies and organisations founded by the League.