The Treaty of Nettuno was an agreement made between the governments of the Kingdom of Italy

Kingdom of Italy (1861–1946)

The Kingdom of Italy was a state forged in 1861 by the unification of Italy under the influence of the Kingdom of Sardinia, which was its legal predecessor state...

 and the Kingdom of Yugoslavia

Kingdom of Yugoslavia

The Kingdom of Yugoslavia was a state stretching from the Western Balkans to Central Europe which existed during the often-tumultuous interwar era of 1918–1941...

 in 1928 which permitted Italians to freely immigrate into Yugoslavia's coastal region of Dalmatia

Dalmatia

Dalmatia is a historical region on the eastern coast of the Adriatic Sea. It stretches from the island of Rab in the northwest to the Bay of Kotor in the southeast. The hinterland, the Dalmatian Zagora, ranges from fifty kilometers in width in the north to just a few kilometers in the south....

 (now part of modern-day Croatia

Croatia

Croatia , officially the Republic of Croatia , is a unitary democratic parliamentary republic in Europe at the crossroads of the Mitteleuropa, the Balkans, and the Mediterranean. Its capital and largest city is Zagreb. The country is divided into 20 counties and the city of Zagreb. Croatia covers ...

). The treaty was made to solve a long-standing territorial dispute between Italy and Yugoslavia over Dalmatia. Many saw the deal as a Yugoslav concession to Italy due to Yugoslavia having a substantially weaker military than Italy at the time.. Yugoslavs - especially Croats - were infuriated with the decision of the Yugoslav government with the treaty calling it treasonous.