Lecourbe's offensive began on 14 August when six columns of French infantry advanced on the upper Reuss valley from the north and east.

By 16 August, Lecourbe's forces had driven Simbschen's Austrians from the valley and seized control of the strategic Gotthard Pass between Italy and Switzerland.

Masséna sent the divisions of Jean-de-Dieu Soult and Joseph Chabran to attack other Austrian positions in order to prevent Archduke Charles from interfering with Lecourbe's main operation.

He acted more vigorously to drive the insurgents out of the upper Reuss valley, by storming their trenches at Flüelen and again at Wassen on 11 May.

Soult seized the Teufelsbrücke (Devil's Bridge) in Schöllenen Gorge before the rebels could break it down and overran the insurgent position at the Gotthard Pass.

On 15 May, his troops met soldiers of Michel Ney's brigade of Lecourbe's division at Faido on the upper Ticino River.

On the Allied side, Heinrich von Bellegarde's Austrian corps marched from the upper Rhine valley south via Lake Como to Alessandria which it reached on 8 June.

[5] To replace these troops, the Allied commander-in-chief in Italy, Suvorov ordered Karl Joseph Hadik von Futak and 16 battalions to the north and the leading formations began moving across the Gotthard Pass on 27 May.

[6] Two days later, Franz Xaver Saint-Julien with 6,300 Austrian soldiers defeated Louis Henri Loison and 3,300 French troops in the Urseren valley.

[6] On 4 June, Archduke Charles commanding 53,000 Austrians attacked Masséna who led 45,000 French in the First Battle of Zurich.

Technically under Massena were the divisions of Claude Juste Alexandre Legrand (6,186) and Claude-Sylvestre Colaud (5,106) guarding the Rhine north of Basel.

[11] Charles told British agent William Wickham that his army could probably drive the French from their positions before Zürich, but it would cost his troops so many casualties that he would be unable to exploit the victory.

[13] During the stalemate, the Austrians grew careless of security, even to the extent of inviting French musicians to play at their dances in Zürich.

[14] Unknown to the French and even to the Austrian and Russian army commanders, Allied strategists were on the verge of making a colossal strategic blunder.

Meanwhile, Archduke Charles would move north into Germany, leaving 18,000 Austrians under Friedrich Freiherr von Hotze to cooperate with the Russians.

[15] On 7 August, when the plan was revealed to Archduke Charles, that general voiced his misgivings about the Russians, "I don't know how they will manage, especially if we take ourselves off any distance".

[16] Masséna decided that recapturing the Gotthard Pass would protect his strategic rear and open communications with the French Army of Italy.

[18] Lecourbe personally accompanied the second column which boated across Lake Lucerne and landed at Flüelen at the head of the upper Reuss valley.

[17] The third column marched along the western shore of Lake Lucerne through Bauen and the Isenthal, meeting Lecourbe at Seedorf.

In the face of this advance, Simbschen withdrew south to the Devil's Bridge where he broke the arch and held his ground.

[17] According to historian Digby Smith, Gudin's 2,400-strong brigade consisted of the 25th Light Infantry Demi-brigade and a Swiss battalion.

[19] In September, the Valais Division had two brigades under Jean-Baptiste Jacopin and Henri-Antoine Jardon and included the 28th, 83rd, 89th, and 101st Line Infantry Demi-brigades, the 1st, 4th, and 5th Swiss Battalions, and the 23rd Horse Chasseur Regiment.

When Simbschen found Gudin's sixth column coming up in his rear, he abandoned the Devil's Bridge and retreated west to the lower slopes of the Crispalt.

On the morning of 14 August, Soult's right brigade under Édouard Mortier crossed the Sihl River at Adliswil and attacked Wollishofen, a suburb of Zürich.

[23] On 15 August, Chabran attacked the brigade of Franz Jellacic and drove it to the east bank of the Linth River.

[24] In the Battle of Amsteg, the French sustained 500 casualties while inflicting 2,300 killed, wounded, and missing on the Austrians and capturing three guns.

On this day, the opposing 5th Division was temporarily led by General of Brigade Étienne Heudelet de Bierre.

Ney, now commanding the neighboring 6th Division, took charge of the defense and massed 12,000 French soldiers to oppose the crossing.

[26] The Russian commander in chief wanted to finish off the defeated French army and clear it from Italy, but the Austrians counseled delay.

Finally, on 25 August Suvorov received a letter from Emperor Francis that his campaigning in Italy was over and that he was to take his army into Switzerland.