<P> President McKinley signed a joint Congressional resolution demanding Spanish withdrawal and authorizing the President to use military force to help Cuba gain independence on April 20, 1898 . In response, Spain severed diplomatic relations with the United States on April 21 . On the same day, the US Navy began a blockade of Cuba . On April 23, Spain stated that it would declare war if the US forces invaded its territory . On April 25, Congress declared that a state of war between the US and Spain had de facto existed since April 21, the day the blockade of Cuba had begun . The United States sent an ultimatum to Spain demanding that it surrender control of Cuba, but due to Spain not replying soon enough, the United States assumed Spain had ignored the ultimatum and continued to occupy Cuba . </P> <P> The ten - week war was fought in both the Caribbean and the Pacific . As the American agitators for war well knew, US naval power proved decisive, allowing expeditionary forces to disembark in Cuba against a Spanish garrison already facing nationwide Cuban insurgent attacks and further wasted by yellow fever . American, Cuban, and Philippine forces obtained the surrender of Santiago de Cuba and Manila despite the good performance of some Spanish infantry units and fierce fighting for positions such as San Juan Hill . Madrid sued for peace after two obsolete Spanish squadrons sunk in Santiago de Cuba and Manila Bay and a third, more modern fleet was recalled home to protect the Spanish coasts . </P> <P> The result was the 1898 Treaty of Paris, negotiated on terms favorable to the US which allowed it temporary control of Cuba and ceded ownership of Puerto Rico, Guam and the Philippine islands . The cession of the Philippines involved payment of $20 million ($588,320,000 today) to Spain by the US to cover infrastructure owned by Spain . </P> <P> The defeat and loss of the last remnants of the Spanish Empire was a profound shock to Spain's national psyche and provoked a thorough philosophical and artistic revaluation of Spanish society known as the Generation of' 98 . The United States gained several island possessions spanning the globe and a rancorous new debate over the wisdom of expansionism . It was one of only five US wars (against a total of eleven sovereign states) to have been formally declared by the US Congress . </P>

One result of the spanish american war of 1898 was that the united states was