"You furnish the pictures, and I'll furnish the war." — William Randolph Hearst, allegedly and semi-quoted in Citizen Kane
"A splendid little war." —John Hay, U.S. Secretary of State
The Spanish-American War of 1898 was what happened when The United States of America tried to conquer most of The Kingdom Of Spain's colonies, i.e. Cuba and the Philippines but not Spanish Morocco or Spain itself.
Through the mid-to-late 19th century, Cuban nationalism and separatism was on the rise. The result, given Spain's utter reluctance to let the colony go, was inevitably violent. Uprisings were attempted, but they were all crushed with varying degrees of brutality. One day, the USS Maine, an American Armored Cruiser sent to implicitly threaten Spain with war if they didn't hurry up and give Cuba to the USA, blew up and sank in Havana Harbor. The US took the opportunity to blame the Spanish, who were quite right to have stated that it was a tragic US Navy accident at best (a result of poor ship-design and notoriously lax safety regulations) and a Wounded Gazelle Gambit at worst. In any case, US President William McKinley was personally reluctant to make a war of the matter, but the US' law-making body - Congress - passed a resolution which effectively forced him to demand that Spain give Cuba 'independence' - which would mean that the USA would effectively run its government and economy just as it did every other nominally-independent country in Latin America bar Argentina - or make it a US Colony. Or else. Though a far weaker country, the Spaniards were a proud people who quietly hoped that the US would just give up on the idea if they put up a good fight. Naturally they refused, and the US declared war upon them.
While Spain's giving up Cuba was the original casus belli, the US ended up demanding the same deal for all of Spain's overseas colonies. The people of Puerto Rico also took the opportunity to demand independence, for instance, as did the peoples of the Philippines - who were already in open revolt and had established a provisional government which the US negotiated with. The US' naval power was employed to great effect, though the performance of the army was a little lacklustre - the US Army were inexperienced and ill-organised, and lost a great many officers due to Spanish snipers using 'smokeless'-powder weaponry (the US Army still used 'black-powder' weapons, which gave off dark clouds of gunpowder when fired). American and Cuban Revolutionary forces soon worked together to make good use of their numerical superiority over the Spanish loyalist and government forces, however. The infamous Charge at San Juan Hill [in which future US President 'Theodore Roosevelt' first attained national fame] and the Battle of Manila Bay, a Curb-Stomp Battle if ever there was one, are good illustrations of the course of the war at large.
Spain soon sued for peace, and a Treaty concluding the war was signed in Paris later in the year of '98. In what was termed domestically as 'the Great Disaster' they ceded Cuba, the Philippines, Guam, and Puerto Rico to the United States. It was a blow to the Spanish national psyche and pride, one which gave birth to a wave of Spanish writers called The Generation of '98. Meanwhile, the Filipinos felt very left out of all this - the negotiations had been concluded without any reference to them or their representatives - and demanded the same independence terms as Cuba. The US refused and a second, more brutal guerilla war ensued as the Americans crushed the provisional Philippine Government and exterminated the rebels while establishing their own 'independent' regime over the islands. The brutal defeat of the uprising, which officially ended in 1902 but there were still incidents for years, is estimated to have killed at least 200,000 Filipinos (with some going much higher) and several thousands of American soldiers as well. Many Americans were actually very much against annexing all of these overseas territories, with the most prominent of them forming the Anti-Imperialist League and including the ranks of such figures as Andrew Carnegie, Samuel Gompers, William James, Jane Addams, Grover Cleveland, and Mark Twain.
The conclusion of the war marked a new height of US National Pride and also the zenith of belief in "Manifest Destiny" - the notion that the US was destined to rule over (all of the) Americas by virtue of its... well, innate virtue and (racial-moral) superiority. The USA's ability to project its influence into the Pacific and China; and Latin America; was of course enhanced by its newest conquests, leading to a period of 'imperialism' (in the bad sense) and events such as US involvement in the Qing Empire's 'Boxer Rebellion' and The Banana Wars.
Tropes involving the Spanish-American War include:
A-Team Firing: American gunnery at the Battle of Manila Bay was embarrassingly horrible. It's estimated that of some 4000 rounds of ammunition fired by Dewey's fleet, only about 2%, or eighty rounds, actually hit the enemy. A stationary enemy. And still the Spanish lost.
Badass: Many on both sides. The Rough Riders of the United States were just one example.
Curb-Stomp Battle: The Battle of Manila Bay. With the sole American casualty due to heat stroke. The Battle at Santiago De Cuba had similar results, with only two American casualties.
The entire war; Spain had long since been a Vestigial Empire, holding on to their last bit of imperial hubris in spite of several rebellions. The United States, on the other hand, was a very large, prosperous, wealthy, and powerful up-and-coming world power. The war was over in less than three months.
A rather hilarious one occurred at the capture of Guam by the USS Charleston. She charged at full speed into the main harbor, firing a challenge salvo at the Spanish in Fort Santa Cruz; the leader of the Spanish garrison abruptly rowed out to the Charleston and apologized for not having any gunpowder to return what HE thought was a saluting gesture, because he had no idea war had been declared. The Charleston proceeded to take him prisoner and the whole barrack surrendered the next day. In the Spanish's defense, news didn't travel very fast back then.
Custom Uniform: The Rough Riders' uniform. Because of shortages of uniforms, the men in this regiment had to do with blue wool uniforms, impractical in the tropical weather of Cuba. It was combined with a campaign hat and a scarf.
End of an Age: The end of four hundred years of Spanish colonial rule in the Americas, dating all the way back to Christopher Columbus. Granted, Spain had already lost most of its colonies by this point, but this is when they finally lost their last ones in the New World. Fittingly enough, it's also the Dawn of an Era — the era in which the United States is one of the world's major powers.
Expanded States of America: The Philippines, Guam, and Puerto Rico were annexed as commonwealths. While the Americans voluntarily and peacefully granted the Philippines independence in 1946, Puerto Rico and Guam remain US territories. Recent polls have shown that they prefer to keep it that way.
Forgotten Trope: Or rather, forgotten war: The wider Cuban and Philippine Wars saw the US fight against the Filipinos for three years, cost 4500 American lives, involved the Spanish and then the US building some of the world's first "concentration camps" (which in fairness were not the horrible death centers of 40 years later but rather extremely uncomfortable and rather degrading spots to "concentrate" the enemy; the British were doing the same thing in South Africa) and numerous atrocities on both sides (which is what inspired Twain to become an anti-Imperialist in the first place).
General Failure: Most historians portray William Shafter, commander of America's expeditionary force to Cuba, in this light. YMMV whether it's entirely fair, given that Shafter succeeded in his task.
Gunboat Diplomacy: The Americans had long-since declared that Latin America was theirs to use as they saw fit. The USA wanted to force the Spanish authorities in Cuba to give them the same deal that they had 'negotiated' with every other Banana Republic in Latin America - no (or very low) taxes on US-owned businesses, no laws promoting local over US-owned business, and no tarrifs on products imported from the USA as per the principle of 'free trade'note This last bit was rather hypocritical. Throughout the 19th and early 20th centuries the USA maintained a 50% tarrif (import-tax) on all non-agricultural goods imported from overseas. Compare Britain, which maintained a tarrif of 0% for the same period. However, Spain was strong (and brave) enough to stand up to the USA - so the USA sent their USS Maine to Havana, Cuba, as a blatant threat that the USA could declare war on them and also in the hope that there would be an incident which the USA could use as a pretext to declare war on them without looking bad. Although it was sent there as a threat and hopefully to cause an incident that would lead to war, its blowing up at anchor there was almost certainly an accident - safety regulations, even regarding things like high explosives, were neither thorough nor properly enforced in a navy as third-rate as the USA's.
History of Naval Warfare: One of the last major wars to feature wooden-hulled (with metal armor) warships fighting against steel-hulled (pre-dreadnought) battleships. This war, combined with the Russo-Japanese War a few years later, could also be seen as a preview of things to come as the two up-and-coming regional naval powers began to expand into the Pacific and Asia...
This was also the first war the United States fought using Battleships, with the USS Texas being the first such ship to enter service (her sister ship, the armored cruiser USS Mainenote classified as a cruiser rather than a battleship due to her main battery having two sets of two 10 inch guns, rather than 2 sets of 12 inch guns, is infamous for being tragically involved with the lead-up to the war due to her accidentally blowing up in Havana Harbor).
Mark Twain: Started out supporting the war, but very quickly became disillusioned. He viewed the Philippine-American War as a great betrayal of both the Philippines and American democratic principles, and was absolutely caustic in his criticism of it. He once suggested a flag for the U.S.-occupied Philippines — "just our usual flag, with the white stripes painted black and the stars replaced by the skull and cross-bones."
Small Reference Pools: When it's lucky enough to be remembered at all, the Spanish-American War consists entirely of Teddy Roosevelt being a Rough Rider and (optional) Hearst's crazy yellow journalism.
Twilight of the Old West: This war was the last one in which the US Army (or some of it) fought in blue uniforms, and many regiments still carried black-powder weapons much like those used in the (just barely over) Indian Wars. Theodore Roosevelt's Rough Rider regiment included many actual cowboys, as well.
The US Army also had veterans of the US Civil War (which had ended about 33 years previously). One of them, Major General Joseph Wheeler, was a former Confederate General and, at the time of the Spanish-American War, was a member of the US Congress. He is reported to have said, while leading US troops, "Let's go, boys! We've got the damn Yankees on the run again!"
Vestigial Empire: Spain, while it ruled a respectable overseas empire, was this. It had already lost Mexico and South America due to a series of revolutions, and was down to only holding Cuba, some other obscure islands, Puerto Rico, someterritory in Africa, and (most importantly) the Philippines. Its swift defeat in this war and the subsequent "Banana Wars" was a clear sign that the United States was the next-most powerful country in The Americas to Britain, whom (due to having twice her population, not to mention oodles of resources) she would soon surpass.
Wake-Up Call Boss: Even though the war was a quick American victory, the poor performance of the army in certain battles caused the government to sink more money into modernizing them.
War Is Hell: During the Battle at Santiago De Cuba, the Spanish armored cruiser Viscaya was fatally damaged after a long running battle against the American North Atlantic Squadron and Flying Squadron. As the crewmen of the USS Texas looked on and cheered, their captain shouted them down:
Captain John Woodward Philip: Don't cheer boys! Those poor devils are dying.