The treaty came into force on April 11, 1899, when the ratification documents were exchanged.  It was the first treaty negotiated between the two governments since the Adams-Ons Treaty of 1819. There was a state of war between Spain and the United States, and all diplomatic relations were suspended. US President William McKinley has ordered a blockade of Cuba. January Andrés Bonifacio chose the supremo of Katipunan, the secret revolutionary society. During the negotiations between the Dewey camp and Demines, the commander of the VIII Corps in San Francisco, Wesley Merritt, shared his views on the Filipinos. In an 1899 interview, Merrit told a reporter from the New York Sun that he had come “with orders not to deal with the Indians [sic]; Do not recognize them and promise nothing,” the general added: “Aguinaldo is for me as much as a boy in the street.” The Spanish commander had a similar attitude; He is “ready to surrender to the whites,” but never to the Filipinos. On July 7 Andrés Bonifacio founded the Katipunan, a secret nationalist fraternal fraternity founded to gain independence from the Philippines by the armed revolution in Manila. Believing that the League was ineffective and too slow to bring about the desired changes of government, Bonifacio, an uneducated storekeeper, decided that the problem in the Philippines could only be solved by force. The Katipunan replaced the peaceful citizens` association that Rizal had founded.
While the Americans were massing their troops, Philippine resistance leader Emilio Aguinaldo announced the resumption of his fight against Spain. Aguinaldo lived in self-imposed exile as part of an agreement with the Spanish authorities, but he turned to the Americans and offered his help in their military campaign. Transported by an American ship from Hong Kong, Aguinaldo landed in Cavite on May 19, gathered his supporters and quickly conquered several towns south of Manila. On 12 June, he proclaimed the independence of the Philippines and was declared President of the Philippine Republic. Aguinaldo`s actions were not sanctioned by the Americans, but there was little they could do to slow his progress. At the head of a large insurgent army, Aguinaldo established a narrow siege of Manila. 29 April The Portuguese government has declared itself neutral in the conflict between Spain and the United States. THE UNITED STATES OF AMERICA AND SA MAJESTY THE REINE REGENT OF SPAIN, TO THE NAME OF THE AUGUST DON ALFONSO XIII, in order to end the war that now exists between the two countries, have designated for this purpose as plenipotentiaries: On September 16, U.S. President William McKinley gave secret written instructions to his emissaries, when the American-Hispanic War : On the other side of the world, a Spanish fleet was put in Santiago in May in the Cuban port of Santiago after crossing the Atlantic from Spain. A superior U.S. naval force arrived a short time later and blocked the entrance to the port.
In June, the fifth U.S. Army Corps landed in Cuba in an effort to march to Santiago and launch a coordinated maritime and ground attack on the Spanish stronghold. Among the American ground troops were the “Rough Riders” led by Theodore Roosevelt, a collection of Western cowboys and Eastern blue blood officially known as the first volunteer cavalry of the United States. On July 1, the Americans won the Battle of San Juan Hill, and the next day they began a siege of Santiago.