Italy–Slovenia border

From Austria to Italy

Before World War I this whole area was Austrian. Trieste was the main port of Austria-Hungary, and in 1910 nearly two-thirds of its people were Italian, the rest mostly Slovenes and Croats. In the secret Treaty of London of 26 April 1915, Britain, France and Russia promised the city to Italy to bring it into the war.^[2]

Gorizia, on the Isonzo river, had been Austrian since 1500. The area saw heavy fighting between Austria and Italy in World War I, and the damaged town was annexed by Italy in 1919.^[3]

Gorizia split, Trieste in limbo

Germany seized Trieste in 1943. In May 1945 the German garrison surrendered to New Zealand troops as Tito’s Yugoslav partisans closed in, and Yugoslavia claimed the city.^[2] The 1947 peace treaty with Italy gave Yugoslavia the northern outskirts of Gorizia, where the new Yugoslav town of Nova Gorica was built.^[3] From 1947 a fence across the square outside Gorizia’s Transalpina railway station marked the border.^[4]

Around Trieste the treaty created a Free Territory under the UN Security Council, split into Zone A, with the city, under US–British military rule and Zone B to the south under Yugoslav administration.^[2] That arrangement never worked. A 1954 agreement gave Zone B and part of Zone A to Yugoslavia and the city and the rest of Zone A to Italy.^[2]

The Treaty of Osimo, signed on 10 November 1975, fixed the part of the frontier the 1947 treaty had left undefined, including the line in the Gulf of Trieste, and ended the 1954 memorandum. It came into force on 3 April 1977.^[1] With it Italy gave up all claims to Zone B.^[2]

“The part of the frontier between the Italian Republic and the Socialist Federal Republic of Yugoslavia not indicated as such in the Treaty of Peace with Italy of 10 February 1947 is described in the text in annex I and plotted on the map in annex II to this Treaty.”^[1]

Borderless, mostly

The square was rebuilt for Slovenia’s entry into the European Union on 1 May 2004, and the fence came down that year, after 50 years. The square, which Slovenians call Trg Evrope and Italians Piazza della Transalpina, now has a mosaic where the line runs.^[4] In 2025 Nova Gorica and Gorizia became the first cross-border European Capital of Culture, under the slogan “GO! Borderless”.^[5]

Italy reintroduced checks on the land border on 21 October 2023, citing the threat of violence after the attack on Israel and migration along the Balkan route; in Friuli Venezia Giulia alone, 16,000 people had been found entering illegally that year.^[6] Italy renewed them repeatedly. In September 2026 its foreign minister said Rome was considering replacing them with agreed measures such as joint patrols when the current extension ends on 18 December 2026.^[7]