The roots of the battle lay in an impossible situation. Filipino forces under General Emilio Aguinaldo had fought alongside the Americans to oust Spain from the Philippines during the Spanish-American War of 1898. But when the Spanish surrendered Manila to the Americans that August, the Filipinos found themselves shut out of the city they had helped liberate. Aguinaldo's troops, an estimated 20,000 strong, encircled Manila along the old Spanish defensive perimeter known as the Zapote Line. Inside the perimeter, some 20,000 American soldiers held positions. The two armies watched each other across blockhouses and trenches, tension building through months of uneasy proximity. Incidents flared around the San Juan Bridge. Both sides knew the arrangement could not hold.

When the shooting started, the Filipino army was effectively leaderless. General Antonio Luna was visiting family in San Fernando. General Mariano Noriel was in Paranaque preparing for his wedding. General Artemio Ricarte and Colonel Luciano San Miguel were in Malolos conferring with Aguinaldo himself. Only General Pantaleon Garcia remained at his post in Maypajo, north of Manila. The American forces, by contrast, were ready - positioned according to previously prepared plans, needing only the order to advance. This asymmetry shaped everything that followed. Caught unprepared in their trenches, Filipino soldiers exchanged fire through the night but could mount only piecemeal resistance. One Filipino battalion did charge the 3rd U.S. Artillery, routing an American company and briefly capturing two artillery pieces - a flash of what organized resistance might have achieved.

Aguinaldo, away in Malolos when the fighting erupted, learned of the battle from a Filipino captain's telegraph. He tried to stop it, sending an emissary to General Elwell Otis on February 5 with the message that the firing "had been against my order." Otis refused to negotiate. A veteran of the American Indian Wars, he saw the moment as one for decisive force: "Fighting having begun, must go on to the grim end." Brigadier General Arthur MacArthur advanced from the north, seizing the ridge overlooking Manila. General Thomas Anderson struck from the south, capturing the village of Pasay. Brigadier General Pio del Pilar's forces, caught between Anderson's advance and the Pasig River, fled into the water, where many drowned. The Filipinos had expected Manila's citizens to rise up and divide the American forces. A few fires were set in the city, but no general uprising came. The provost guard under Brigadier General Robert Patterson Hughes suppressed the disturbances quickly.

The battle of February 5 was the largest and bloodiest engagement of the entire Philippine-American War. American casualties totaled 238, with 44 killed in action or dead from wounds. Filipino losses were far greater, though precise numbers remain disputed - photographs from the period show trenches filled with the dead near Santa Ana. The battle shocked the Filipino forces, who had grown accustomed to Spanish tactics of retreating into fortified cities after nighttime raids. The American advance was something different: relentless, coordinated, and aimed at total military victory. What followed was not a quick campaign but a grinding three-year war of guerrilla resistance and counterinsurgency that would claim an estimated 200,000 to 1,000,000 Filipino civilian lives, many from war-related famine and disease.

Today, a memorial marker in Manila marks the spot where the war began - though recent scholarship by Ronnie Miravite Casalmir has established that the marker sits at the wrong intersection. Grayson fired at the corner of Sociego Street and Tomas Arguelles Street, not at Sociego and Silencio where the monument was placed. The evidence comes from Grayson's own reenactment photograph, which shows Blockhouse 7 in the background, and from Lieutenant Wheedon's distance estimates placing the patrol route at the Arguelles corner. It is a fitting irony for a war that began with confused signals in the dark: even the memorial remembering its first shots cannot quite locate them.