First Italian campaign

Two days after the marriage, Bonaparte left Paris to take command of the Army of Italy and led it on a successful invasion of Italy. At the Battle of Lodi he defeated Austrian forces and drove them out of Lombardy. He was defeated at Caldiero by Austrian reinforcements, led by József Alvinczi, though Bonaparte regained the initiative at the crucial Battle of the Bridge of Arcole and proceeded to subdue the Papal States. Bonaparte argued against the wishes of Directory atheists to march on Rome and dethrone the Pope as he reasoned this would create a power vacuum which would be exploited by the Kingdom of Naples. Instead, in March 1797, Bonaparte led his army into Austria and forced it to negotiate peace. The Treaty of Leoben gave France control of most of northern Italy and the Low Countries, and a secret clause promised the Republic of Venice to Austria. Bonaparte marched on Venice and forced its surrender, ending 1,100 years of independence; he also authorised the French to loot treasures such as the Horses of Saint Mark.

Bonaparte at the pont d'Arcole, by Baron Antoine-Jean Gros, (ca. 1801), Musée du Louvre, Paris

His application of conventional military ideas to real-world situations effected his military triumphs, such as creative use of artillery as a mobile force to support his infantry. He referred to his tactics thus: "I have fought sixty battles and I have learned nothing which I did not know at the beginning. Look at Caesar; he fought the first like the last." He was adept at espionage and deception and could win battles by concealment of troop deployments and concentration of his forces on the 'hinge' of an enemy's weakened front. If he could not use his favourite envelopment strategy, he would take up the central position and attack two co-operating forces at their hinge, swing round to fight one until it fled, then turn to face the other. In this Italian campaign, Bonaparte's army captured 150,000 prisoners, 540 cannons and 170 standards. The French army fought 67 actions and won 18 pitched battles through superior artillery technology and Bonaparte's tactics.
During the campaign, Bonaparte became increasingly influential in French politics; he founded two newspapers both for the troops in his army and also for circulation in France. The royalists attacked Bonaparte for looting Italy and warned he might become a dictator. Bonaparte sent General Pierre Augereau to Paris to lead a coup d'état and purge the royalists on 4 September—Coup of 18 Fructidor. This left Barras and his Republican allies in control again but dependent on Bonaparte who proceeded to peace negotiations with Austria. These negotiations resulted in the Treaty of Campo Formio, and Bonaparte returned to Paris in December as a hero. He met with Talleyrand, France's new Foreign Minister—who would later serve in the same capacity for Emperor Napoleon—and they began to prepare for an invasion of England.