The United Provinces of New Granada had declared independence from Spain in 1811, and by 1815 controlled much of present-day Colombia. But Napoleon's defeat in Europe freed King Ferdinand VII to turn his attention to the colonies, and in 1815 he dispatched General Pablo Morillo with a large fleet to restore Spanish authority. Morillo's strategy was a pincer: he would besiege the port city of Cartagena de Indias from the north while Colonel Sebastian de la Calzada invaded from Venezuela through the eastern plains. Calzada's 5th Division, some 2,200 men with infantry, cavalry, and artillery, crossed into New Granada in October 1815. The only republican force in his path was Brigadier Joaquin Ricaurte Torrijos with 150 infantry and 1,000 cavalry. Though Ricaurte won the initial clash at the Battle of Chire on October 31, his cavalry paused to loot instead of pursuing, and Calzada's army escaped to fight again. It was the kind of lost opportunity that would define the entire campaign.

Bad intelligence compounded the republicans' problems. After Chire, Ricaurte reported that Calzada had only 400 troops in poor condition. The real number was closer to 2,000. General Rafael Urdaneta, relying on this faulty estimate, gathered 1,000 men to intercept Calzada at the Chitaga River. When the two forces met at the Battle of Balaga on November 25, the republicans discovered their error fatally late. Only 200 of Urdaneta's soldiers escaped the defeat. Calzada occupied Pamplona, cutting off republican forces to the north, including Colonel Santander's veteran 5th Line Battalion stationed in Ocana. Trapped between Morillo's forces to the north and Calzada to the south, Santander executed a skillful retreat through abandoned mountain paths to Piedecuesta, where Brigadier General Custodio Garcia Rovira was assembling the Army of the North. It was an impressive piece of soldiering from a man who would one day become Colombia's president.

Rovira positioned his 2,000 infantry and 80 cavalry in three defensive lines on the Paramo de Cachiri, guarding the road to Bucaramanga and the Socorro province beyond. Santander, his second-in-command, protested the plan, arguing that novice troops mostly armed with lances rather than muskets were poorly suited for static defense. Rovira overruled him. On February 21, Calzada's reinforced army attacked. The first day went reasonably well for the republicans. Colonel Pedro Arevalo's battalion held the right flank against Spanish flanking attempts, and nightfall halted the fighting with Rovira's lines intact. Emboldened, Rovira pulled back to a second set of defensive positions. The next morning, Calzada launched a coordinated assault: flanking columns of elite cazadores on both wings, supported by a four-pound cannon, while grenadier companies from the Numancia and Sagunto battalions advanced on the center with volley fire.

The collapse came fast. When the Santafe Battalion's commanding officer was killed by converging musket and artillery fire, his troops abandoned their trench. The Tunja Battalion behind them was supposed to fill the gap but withdrew instead. A third battalion followed, and the retreat became general panic. Santander ordered his veteran 5th Battalion to fire on the advancing Spanish, but before they could reload, fleeing soldiers from the forward battalions swarmed through their ranks. Calzada unleashed his cavalry, and the rout became a massacre that continued all the way to the town of Matanza, where a river finally stopped the pursuit. The Army of the North ceased to exist. Calzada reported roughly 1,000 republican dead and 500 prisoners, many of whom were pressed into Spanish service. News reached Bogota on February 29. Garcia Rovira was relieved of command on March 7. President Camilo Torres resigned on March 12. The first republic was finished. Three years later, Santander and Bolivar would return to fight for independence again, and this time they would win. But the road through Cachiri's paramo remembers the cost of the first attempt.