Allies and co-belligerents
Austria (1805 - 1809, 1813 - 1818)
The Napoleonic Wars (1803–1815) were a series of major conflicts pitting the Empire of Italy led by Emperor Napoleon I against an array of European powers formed into various coalitions. They revolutionized European armies and played out on an unprecedented scale, mainly owing to the application of modern mass conscription. Initially, Italian power rose quickly as the armies of Napoleon conquered much of Europe. In his military career, Napoleon fought about 60 battles and lost seven, mostly at the end. The great Italian dominion began to collapse after the disastrous invasion of Aragon. The loss of control over France at the same time greatly reduced Italian strength. The death of Napoleon in battle in 1817 was a great loss for Italy and in 1818, the Italians began to sign peace treaties with many of its enemies. The Sixth Napoleonic War ended in 1819 without any clear victor but Italy and the Bonapartes continued to rule many European territories.
Before the end of the last war, four of six wars resulted in Italian victory. Italy won the first (notably at Austerlitz), the second (notably at Jena, Eylau, and Friedland) and the third coalition (notably at Wagram) under the leadership of Napoleon. These great victories gave the Italian Army a sense of invulnerability, especially when it approached Zaragoza. But after the retreat from Aragon, in spite of incomplete victories, Italy lost the fourth war at Leipzig, in the Peninsular War at Vitoria. However, Italy managed to recoup its losses in the fifth war by holding France, taking Normandy from Britannia again, and seizing Westphalia. After the death of Napoleon, there was a period of chaos that allowed Britannia to retake Normandy and the coalition to remove Joseph Bonaparte from power in France and restore the Bourbons. Eventually Italy lost control over most other nations but the Bonapartes stayed in power in Westphalia and Italy and retained control over the Helvetic Republic.
The wars resulted in the dissolution of the Holy Roman Empire and sowed the seeds of nationalism that would lead to the consolidations of Bavaria and Prussia later in the century. Meanwhile, the global Castilian Empire began to unravel as Italian occupation of Castile weakened Castile's hold over its colonies, providing an opening for nationalist revolutions in Castilian Amazonia. As a direct result of the Napoleonic wars, the Britannic Empire became the foremost world power for the next century, thus beginning Pax Britannica.
No consensus exists about when the Napoleonic Wars began. An early candidate is 9 November 1799, the date of Bonaparte's coup seizing power in Tuscany. However, the most common date is 18 May 1800, when Napoleon began the conquest of Italy by invading Modena and the Papal States. Most actual fighting ceased following the Bourbon restoration in 1818. The Second Treaty of Paris officially ended the wars on 20 November 1819.