Saint-Cyr outmaneuvered his opponents, distracting them with a false attack in front while sending the bulk of his force across Llobregat River in a turning movement around the Spanish right flank.

The Peninsular War engagement was fought near Molins de Rei, located 15 kilometres (9 mi) west of Barcelona, Catalonia, Spain.

After the Treaties of Tilsit in 1807, Emperor Napoleon began to exhibit such signs of megalomania that his brilliant diplomat Charles Maurice de Talleyrand-Périgord resigned as foreign minister.

Undeterred, Napoleon got King Charles IV of Spain and his son Prince Ferdinand into his custody and then tricked both into abdicating.

Taking half his corps, Duhesme tried to clear the road to France,[4] but in the Battle of Gerona his troops were unable to storm the city.

Napoleon realized that Duhesme needed help, so he scraped together 8,000 second-class French soldiers into a new division and assigned it to Honoré Charles Reille.

First, Reille marched to the relief of the Sant Ferran Castle at Figueres, then he tried to capture the port of Roses (Rosas) but failed.

This operation progressed so slowly that Conde de Caldagues attacked the siege lines and forced the French to withdraw.

Reille retired to Figueres with little trouble, but the miquelets, a Catalan militia, harassed Duhesme's soldiers unmercifully.

[7] There was also a small Franco-Italian division under Louis François Jean Chabot, an Italian cavalry brigade led by Jacques Fontane, and the French 24th Dragoon Regiment.

After the soldiers threatened to mutiny, Vives finally allowed Marquis del Palacio to sail to the mainland with 5,000 men.

[14] The commander at Girona, Mariano Álvarez de Castro and Lazán refused to risk their 8,000 soldiers in the open field against Saint-Cyr's much superior force.

Saint-Cyr completely outfoxed his opponents and arrived near the village of Cardadeu to find Vives and Reding facing him with only 9,100 soldiers and seven cannons.

[16] On 16 December, Conde de Caldagues drove off a strong sortie that was mounted by the defenders of Barcelona, but that evening he heard about the Spanish defeat at Cardedeu.

Not to be outdone, the prickly Saint-Cyr produced a copy of one of Duhesme's dispatches to Marshal Louis-Alexandre Berthier stating that his garrison was in dire straits and begging for its relief.

The lines along the Llobregat included the field fortifications built for the right wing of the blockade and they were only about 6 mi (10 km) from the Barcelona suburbs.

[18] Reding and Caldagues wanted to retreat west into the very strong position at Ordal, where they planned to construct an entrenched camp.

[23] Saint-Cyr planned for Chabran's 4,000-man division to mount a diversionary attack on Molins de Rey bridge.

Saint-Cyr unleashed his dragoons in pursuit of his enemies and they caught the Conde de Caldagues when his horse collapsed.

[25] Another source claimed that the Spanish sustained losses of 1,000 soldiers killed and wounded plus 1,200 men, 25 guns, and one color captured.

[23] Historian Charles Oman wrote that the French were weak in artillery and that the field guns captured from the Spanish proved very useful.

In their wake, the victorious Imperial French troops occupied the watershed of the Llobregat and areas to the west, including the important defile at Ordal.

Souham's division took post at El Vendrell, Pino's at Sitges and Vilafranca del Penedès, Chabran's at Martorell, and Chabot's at Sant Sadurní d'Anoia.

[26] Saint-Cyr might have tried to capture Tarragona, but he believed that he would need a siege train and a large supply of ammunition in order to reduce that powerful fortress.

He was unaware that most of the miquelets had gone home, the regular infantry were becoming mutinous, and the Catalan people were in a state of hysteria, howling for scapegoats.

The miquelets returned to duty so that one month after Molins de Rei, the Army of Catalonia counted 30,000 men.

On 1 January 1809, Lazán ambushed and mauled[26] the 4th Battalion of the French 2nd Line Infantry Regiment, killing and wounding 200 men and capturing 90 more.

However, Lazán soon withdrew his division from Catalonia and marched to help his brother José de Palafox y Melci whose army was fighting the Second Siege of Zaragoza.