Today is Liberation Day in Italy. It is a day to celebrate the surrender of German troops occupying Italy and liberating the country with the help of the Allied Forces.
In 1944, with the Allied forces nearby, the partisan resistance in Italy staged an uprising behind German lines, led by the Committee of National Liberation of Upper Italy (CLNAI). This rebellion led to the establishment of a number of provisional partisan governments throughout the mountainous regions of northern Italy, of which Ossola was the most important and received recognition from Switzerland and from Allied consulates in Switzerland. By the end of 1944, German reinforcements and Benito Mussolini's remaining forces had crushed the uprising, and the area's liberation had to wait until the final offensives of 1945.
After a few months of reorganization, another massive uprising was planned. On April 25, 1945, concurrent with the renewal of the Allied offensive, the CLNAI called out a general insurrection. This insurrection ended with the surrender of German forces in Italy and the liberation of most Italian cities.
You can find more information about the Italian resistance movement at this site.