After the American victory in Manila Bay on May 1, 1898, the United States Navy, under Admiral George Dewey, blockaded the city of Manila and waited for land forces to arrive. The United States organized the Eighth Army Corps, dubbed the Philippine Expeditionary Force, under the command of Major General Wesley Merritt. On May 16, the vanguard of the force left San Francisco under the command of Brigadier General Thomas M. Anderson. Merritt, on the same day, asked for information concerning the strength of the Spanish in the Philippines. The American consul in Hong Kong gave the information needed: 21,000 men including 4,000 Filipinos, all but 1,000 of them in Manila. Dewey, however, sent more accurate information: around 40,000 troops including around 16,000 Filipinos, about 15,000 were situated in Manila, and nine artillery guns in Manila. By mid-June, some 40,000 Filipino revolutionaries under General Antonio Luna had dug fourteen miles of trenches around Manila. Filipino revolutionaries, seizing control of Manila's only pumping station, cut off the water supply to the city.
The first contingent of American troops arrived in Cavite on June 30, the second under General Francis V. Greene on July 17, and the third under General Arthur MacArthur on July 30. By this time, some 12,000 U.S. troops had landed in the Philippines.
Emilio Aguinaldo had presented surrender terms to Spanish Governor-General of the Philippines Basilio Augustín, who refused them initially, believing more Spanish troops would be sent to lift the siege. As the combined forces of Filipinos and Americans closed in, Augustín, realizing that his position was hopeless, secretly continued to negotiate with Aguinaldo, even offering ₱1 million, but the latter refused. When the Spanish parliament, the Cortes, learned of Governor-General Augustín's attempt to negotiate the surrender of the army to Filipinos under Aguinaldo, it was furious, and relieved Augustín of his duties as Governor-General, effective July 24, to be replaced by Fermin Jáudenes. On June 16, warships departed Spain to lift the siege, but they altered course for Cuba where a Spanish fleet was imperiled by the U.S. Navy. In August 1898, life in Intramuros (the walled center of Manila), where the normal population of about ten thousand had swelled to about seventy thousand, had become unbearable. Realizing that it was only a matter of time before the city fell, and fearing vengeance and looting if the city fell to Filipino revolutionaries, Governor Jáudenes suggested to Dewey, through the Belgian consul, Édouard André, that the city be surrendered to the Americans after a short, "mock" battle. Dewey had initially rejected the suggestion because he lacked the troops to block the Filipino revolutionary forces, but when Merritt's troops became available he sent a message to Jáudenes, agreeing to the mock battle.
Merritt was eager to seize the city, but Dewey stalled while trying to work out a bloodless solution with Jáudenes. On August 4, Dewey and Merritt gave Jáudenes 48 hours to surrender, later extending the deadline by five days when it expired. Covert negotiations continued, with the details of the mock battle being arranged on August 10. The plan agreed to was that Dewey would begin a bombardment at 09:00 on August 13, shelling only Fort San Antonio Abad, a decrepit structure on the southern outskirts of Manila, and the impregnable walls of Intramuros. Simultaneously, Spanish forces would withdraw, Filipino revolutionaries would be checked, and U.S. forces would advance. Once a sufficient show of battle had been made, Dewey would hoist the signal "D.W.H.B." (meaning "Do you surrender?), whereupon the Spanish would hoist a white flag and Manila would formally surrender to U.S. forces.