Relations between Italy and the United States have gone through different stages, from the early process of nation-building during the 18th and the 19th centuries, to the close diplomatic and political alignment of the Cold War and the first two decades of the 21st century. Throughout these two and a half centuries, relations between the two states occasionally experienced some difficult moments—from the tensions connected to the mass immigration of Italians to the United States at the end of the 19th century, to the diplomatic clash at the Versailles Peace Conference at the end of World War I, culminating with the declaration of war by the Fascist government in December 1941. By and large, however, Italy and the United States have mostly enjoyed a strong relationship based on close cultural, economic, and political ties.