After the collapse of the Western Roman Empire in the 5th century AD, Italy was not united as one country again until the 1870’s. The country was broken up into states which warred much of the time between each other and became easy prey to ambitious rulers outside.
But in the 19th century, championed by the great Italian statesman Cavour and others, the states began to throw off their former rulers and opted to build a new Italy.
This movement was called the Risorgimento, and Victor Emanuel of Sardinia and Piedmont became the first king of Italy.