1889 – Somalia: the first Italian colony was established in Southern Somalia between 1889 and 1890, initially as a protectorate. In June 1925, the Italian influence was extended to former part of British Kenya and in 1940 the Italian troops occupied the British Somalia, known as Somaliland. But in 1941, British occupied the whole Italian Somalia and re-conquered Somaliland also.
1911 – Lybia: After a fast war against the Ottoman Empire, in 1911 Italy took control on the Lybian regions of Cyrenaica and Tripolitania, which have been then unified in 1934 under the name of Lybia (the old Roman name for the territory). During Fascism Age, Italy have been attempting to “pacify” the colony (against the rebels of Omar Mukhtar), during which gassing campaigns and mass deportations have been severely perpetrated against the original inhabitants. Italy lost control of Libya when German and Italian forces withdrew into Tunisia in 1943. Italians were against the Lybian invasion because they didn't want the government to spend their money to build roads and infrastructures in a land that they claimed was "uno scatolone di sabbia" (a box full of sand). Unfortunately they didn't notice that it was a box full of oil, so when Colonel Qaddafi took power in 1969 after the Green Revolution, he evenly kicked all the remaining Italian asses out of the Country and kept the royalties on petroleum and gas. On the Lybian campaign there is by the way a nice movie from 93 years old Italian director Mario Monicelli: Le Rose del Deserto (2006).
1912 – Dodecanese Island: the islands of Rhodes and the surrounding islands were a territorial gain Italy was able to make at the expense of the enfeebled Ottoman Empire with the Italo-Turkish War of 1911-1912. While the Treaty of Sèvres in 1919 called for most of the smaller islands to join with Greece, with Rhodes and several other islands remaining Italian, later, in 1923, the treaty of Lausanne gave international recognition to the continued Italian administration over the whole group. Two days after the Italian Government reached an armistice with the Allies on 8th September 1943, German forces attacked the Italians on Rhodes, forcing a surrender the next day. Despite the landing of British troops, the Germans seized Kos on October 4 after a day of fighting, and Leros fell to the Germans on November 16 after five days of fighting. You can find some details about this story in the movie Captain Corelli's Mandolin with Nicholas Cage and Penelope Cruz (if you are good enough to get rid of the buttery love story...). Otherwise i suggest Gabriele Salvatores' Mediterraneo (Oscar Winner as Best Foreign Language Film in 1992): w-o-n-d-e-r-f-u-l!
1936 - Ethiopia: in the 1890s the Italian Army, following a previous agreement with the Negus of Ethiopia Menelik, occupied a part of the Ethiopian Highland including the city of Asmara. Italy was defeated in its first attempt to conquer Ethiopia (called Abyssinia by Europeans at that time) in the First Italo-Ethiopian War in 1895-96, but the Italians were able to occupy Ethiopia in the war of 1935-36 after seven months of fighting. Victory was announced on 9th May 1936, when the Italian King Vittorio Emanuele III proclaimed himself “Emperor of Ethiopia” and Benito Mussolini “Founder of the Empire”. At the beginning of 1941 the English troops defeated Italians and occupied Ethiopia, but some flash points of Italian resistance remained active until the autumn of the same year and re-established the former Negus Haile Selassie.i've read an interesting article on the excellent Italian magazine Internazionale last year about the Italian heritage in Ethiopia and Eritrea: in Asmara, Massaua and Addis Abbeba is still plenty of old people speaking Italian and of places built during the Fascism Age with names in Amharic and Italian. I've remembered this article once when i was in Rock Bottom (a club in Abu Dhabi where i used to go) with my friends and the Ethiopian bouncer wanted us to leave even if our glasses were still full. i asked him where he was from and when he told me "Addis Abbeba", i said: "Ah, what a beautiful city!" "Have you been there?" i lied: "Yes, i've spent one week there..." "Really? Where were you staying?" "Oh, do you know that nice hotel near Cinema Impero? i can't remember the name..." "Oh yes, yes! I know it! Then if you were in Addis Abbeba, no need to leave now my friend!"... as you see, we are all brothers and sisters in the end...
Other territories submitted to Italian authority were Montenegro and Dalmatia (in the former Yugoslavia), Tiensin in China, and Nice and Corsica (French territories invaded by Italians during World War II).