A year prior to the war, in the Plombières Agreement, France agreed to support Sardinia's efforts to expel Austria from Italy in return for territorial compensation in the form of the Duchy of Savoy and the County of Nice.

That led Prime Minister Camillo Benso, Count of Cavour to attempt to establish relations with other European powers, partially through Piedmont's participation in the Crimean War.

In the peace conference at Paris after the Crimean War, Cavour attempted to bring attention to efforts for Italian unification.

He found Britain and France to be sympathetic but refusing to go against Austrian wishes, as any movement towards Italian independence would threaten Austria's territory of Lombardy–Venetia.

The assassination attempt brought widespread sympathy for the Italian unity and had a profound effect on Napoleon III himself, who now was determined to help Piedmont against Austria to defuse the wider revolutionary activities, which governments in Italy might later allow to happen.

After a covert meeting at Plombières on 21 July 1858, Napoleon III and Cavour signed a secret treaty of alliance against Austria on 28 January 1859.

The secret alliance served both countries by helping with the Sardinian-Piedmontese plan of unification of the Italian Peninsula under the House of Savoy.

Cavour, being unable to get French help unless the Austrians attacked first, provoked Vienna by a series of military maneuvers close to the border.

However, Count Gyulai, the commander of the Austrian troops in Lombardy, was very cautious and marched around the river Ticino in no specific direction until he crossed it to begin the offensive.

Unfortunately for him, very heavy rains began to fall, which allowed the Piedmontese to flood the rice fields in front of his advance and slowed his army's march to a crawl.

The Franco-Sardinian move to strengthen the Alessandria and Po bridges around Casale Monferrato forced the Austrians to halt their advance on 9 May and to fall back on 10 May.

During the retreat, the Austrians won one of their only victories of the war, when Karl von Urban defeated Giuseppe Garibaldi at the Battle of Treponti.

Ludwig von Benedek with the Austrian VIII Corps was separated from the main force and defended Pozzolengo against the Piedmontese part of the opposing army.

[6] Meanwhile, in the north of Lombardy, the Italian volunteers of Giuseppe Garibaldi's Hunters of the Alps defeated the Austrians at Varese and Como, and the Piedmontese-French Navy landed 3,000 soldiers and conquered the islands of Losinj (Lussino) and Cres (Cherso), in Dalmatia.

The agreement, made by Napoleon behind the backs of his Sardinian allies, led to great outrage in Piedmont-Sardinia, and Cavour resigned in protest.

Austria had emerged triumphant after the suppression of liberal movements in 1849, but its status as a great power on the European scene was now seriously challenged and its influence in Italy severely weakened.

[10] These reforms were the basis for Prussia's rapid victories over Austria in 1866 and France in 1870-71, which led to a united Germany under Prussian dominance.