Please look at the excellent article Italians in WWII, by Justin Demetri
The years from 1940 to 1945 in Italy, as well as in many other countries of the world, were those of the Second World War. The Italian military effort in those years has been often criticized: while the army of Italy was thought to have poorly performed during the war, this was mainly because of the circumstances at the time.
For Italy, it all began in June 1940, when the French government declared Paris an open city after German armies invaded the country. At the time, Mussolini felt the war would not have lasted long, and declared war on France and Britain. Mussolini had the aim of expanding colonial holdings of Italy in North Africa, by taking colonies from France and Britain.
The Attack on France
The Italians launched their first attack on France in June, 1940. After being successful initially, they stalled at the Alpine Line. France surrendered to Germany in the same month, and Italy captured a few areas of France along the Italian–French border.
In November 1942, the Italian army invaded again South-eastern France and Corsica. From the following month, an Italian military government was established on the east side of Rhone River. This continued until September when Italy decided to quit the war against France.
North African Campaign
Italy never really experienced any achievements in North Africa. Within a week of declaring war in 1940, the British had seized Fort Capuzzo in Libya. Throughout its permanence on North African soil, the Italian army experienced several sets back and numerous logistic issues, often solved only by the intervention of better equipped and better lead German troops.
Battle of Britain
Dictator of Italy, Benito Mussolini, intended to support the German effort on the British front during the Battle of Britain. The contingent from the Italian Royal Air Forces (La Regia Aeronautica) set to participate to the Battle of Britain were known as CAI, il Corpo Aereo Italiano, or Italian Air Corps. The CAI travelled to Belgium in 1940 and first attacked in October of that year. Italian aircrafts had joined fights towards the end of the battle.
All of the equipment used by the Italian Air Corps was obsolete and could not match to that of Britain or Germany. Due to this, Italy did not gain much success during the battle.
Along with several other well known battles in 1940, the Italians also started their East African campaign in June. The front had been opened from their colonies in East Africa: Eritrea, Somalia and Ethiopia. Like in Egypt, the Italian forces joined hands with the native army and outnumbered the British troops. However, Italian East Africa was far away from the mainland: this resulted in the forces being cut off from their supply, causing the ultimate halting of operations in the area.
During the early East African attacks, two different methods were adopted: first, attacks were held both towards Kenya and Sudan. Later, in August, Italian troops advanced in Somalia, a land once owned by the British. After a few casualties, British troops were evacuated from the region by the Italian forces.
Even before Italy declared war, Mussolini had shown great interest to the lands of Albania. At the beginning of 1939, while the other countries were only focused on Hitler’s advances on Czechoslovakia, Italian troops attacked Albania in April. In spite of a strenous resistance from the natives, Italy was able to quickly take control of the country.
Invasions of Italy
In July 1943, the British and American troops joined hands and attacked Sicily in an operation known as Operation Husky. The German troops took up the cause and helped Italy defend the attacks. Though they lost Sicily to the allies, they did succeed in sending a large number of Italian and German forces to safety from Sicily onto the mainland.
Later that same month, an air raid on Rome caused havoc in the city, provoking destruction on military as well as civil and historical sites. With these attacks, the people of Italy, demoralised and hungry, felt less and less to support the war effort of their country. In July 1943, the Italian dictator Mussolini was ousted by the Grand Council of Fascism. The new government, which had been led jointly by the popular King, Victor Emmanuel III and Pietro Badoglio, took over the power, after having abandoned, however, the capital.
The Royal Italian government based in Puglia (not to be mistaken with the Fascist Republic of Salò ruling the North of the country) soon began secret negotiations with the allies to bring an end to the war. This was mostly dedided because of the dire situation of Italian population and because of the achieved awareness the army was not in a state fit to fight a war. In September 1943 an armistice was secretly signed between Italy and the allies at the Fairfield Camp located in Sicily. This had been announced a few days later. By this time the allies were already in mainland Italy.
Winston Churchill had always regarded southern European countries to be military and politically weak: during the First World War, he advocated in favor of the Dardanelles operation and then later, during the Second World War he supported the idea of creating a main operative area in the Balkans. Churchill had called Italy the soft underbelly of the continent and had therefore decided to invade the country.
However, Italy proved not to be an easy target for the forces. Due to the rugged mountain terrain the Italian troops had excellent positions for defense; however, it did ignore the advantage that the allies had in terms of mechanized and motorized weapons and units.
The final victory of the allies over the axis in Italy did not happen until the spring of 1945. This happened when the allies had crossed the Gothic Line. This resulted in the surrender of all German forces on Italian soil. With this, the Second Word War finally ended for Italy.