Garibaldi's troops tried to capture Rome, which was at that time the main Italian city not yet incorporated into the newly unified Kingdom of Italy.

However, the Italian government could not take its seat in Rome because Emperor Napoleon III maintained a French garrison there to prop up Pope Pius IX.

Opposition to the expedition was forced on the Italian government by Napoleon III, who threatened military intervention if Garibaldi were not stopped.

This unpopular agreement led to numerous riots (primarily in Turin which objected to its loss of status) and to renewed demands for the Italian government to take possession of its capital, Rome.

A small contingent, led by Enrico Cairoli with his brother Giovanni and 70 companions, made a daring attempt to take Rome.

In the meantime, Giuseppe Monti and Gaetano Tognetti let explode a mine under the Serristori barracks in Borgo, which was the seat of the Papal Zouaves, devastating the building and killing 27 persons.

At the summit of Villa Glori, near the spot where Enrico died, there is a plain white column dedicated to the Cairoli brothers and their 70 companions.

About 100 metres (110 yd) to the left of the top of the Spanish Steps, there is a bronze monument of Giovanni holding the dying Enrico in his arm.

The Papal vanguard met Garibaldi's volunteers about 1.5 kilometres (0.9 mi) south of the village Mentana, midway between Rome and Monterotondo.

In Mentana, the monument Ara dei Caduti (Altar of the Fallen) is built over the mass grave of the Italian patriots who died in the battle.

Rome was captured by the Italian Army on September 20, 1870, finally giving Italy possession of its capital and concluding the Unification.