Brigadier General Henry Hopkins Sibley had marched his Army of New Mexico north from Texas with an audacious plan: seize the territory, push through to Colorado's gold fields, and potentially reach the Pacific coast to open Confederate access to western ports. The campaign began with a Confederate victory at Valverde in February 1862, and Sibley's Texans briefly occupied Albuquerque and Santa Fe. But at Glorieta Pass on March 28, Union forces destroyed Sibley's supply train in what became known as the Gettysburg of the West. Without supplies, the Confederate invasion collapsed. By early April, Sibley's men were in full retreat down the Rio Grande valley, pursued by Canby's forces. Colonel Green's regiment found itself camped in Peralta, separated from the rest of the Confederate army across the river in Los Lunas.

Canby struck at dawn. Union cavalry charged the Confederate wagon train on the outskirts of town, killing and capturing the guards. Green's Texans scrambled into defensive positions behind Peralta's low adobe houses, turning the town's mud-brick walls and irrigation canals into improvised fortifications. Canby captured a Confederate supply train approaching from outside town, then dispatched Colonel John Chivington and Colonel Gabriel R. Paul to encircle the Texans and cut off any reinforcements. But when Canby assessed the Confederate defenses - thick adobe walls reinforced by a network of irrigation ditches - he judged the position too strong to storm without unacceptable losses. Across the Rio Grande, General Sibley heard the fighting and led the 4th and 7th Texas Mounted Rifles to the river's edge. The two sides settled into an artillery duel, cannons booming across the flat New Mexico landscape, reducing the town of Peralta to rubble.

Then the land itself took a hand. A massive dust storm rolled across the Rio Grande valley, blinding both armies in a wall of brown grit. Visibility dropped to almost nothing. Under this curtain of sand, the Confederates slipped out of their battered positions and crossed to the west bank of the Rio Grande, rejoining Sibley's main force. They reached Los Lunas at four in the morning, rested for a few exhausted hours, and resumed their retreat south toward Texas. Canby followed with his army, harassing the Confederate column with cavalry, but never forced another major engagement. The Union commander seemed content to let the broken Confederates leave New Mexico rather than risk a pitched battle that might cost more lives on both sides.

Peralta was one of the final engagements of the New Mexico Campaign, a brief but significant chapter of the Civil War that determined the fate of the American Southwest. Had Sibley's gamble succeeded, the Confederacy might have gained access to western gold, Pacific ports, and the loyalty of territories stretching from Texas to California. Instead, his army limped back to San Antonio with roughly half the men it had started with, many of them barefoot and starving. The town of Peralta itself bore the scars - its adobe buildings reduced to rubble by artillery fire from both sides. Today, the small community sits quietly along the Rio Grande in Valencia County, about 20 miles south of Albuquerque, with little visible trace of the day two armies battered each other among its irrigation ditches while the desert decided the outcome.