On this day in 1898, the USS Maine sunk in Havana harbor, in the Spanish colony of Cuba. American public opinion immediately blamed the Spanish authorities, who were in the process of fighting a Cuban rebellion that had widespread sympathy in America.
This quickly led to war with Spain, and the United States gaining most of Spain's colonies - and gaining global influence.
The Maine was, really, an excuse for the powder-keg of war that had already been brewing.
For about as long as America had been a nation, Americans had been sympathetic to revolutions against colonial rule, especially in Latin America. After most of Latin America had thrown off Spanish and Portuguese rule in the early 1800's (with American sympathy though little actual help), Cuba and Puerto Rico were Spain's two remaining American colonies.
In the 1890's, Cuba was suffering. It had only recently abolished slavery - in 1886, the next-to-last place in the Americas - and the economy hadn't found a new structure yet. In part because of this, a bloody guerilla rebellion had been festering for years that Spain hadn't quite been able to suppress. Unsurprisingly, the rebels had a lot of sympathy in the United States. The Maine was in Havana harbor in the first place as a warning to the Spanish authorities.
And then, the Maine exploded.
My best guess is it was a coincidence. Coal dust in the coal bunkers was known to cause steamships to explode in that era, and a 1970's US Navy historical investigation agreed that was the most likely reason. However, that really didn't matter for the war. American journalists immediately blamed Spain, a US Navy investigation quickly agreed (on March 28th), and Congress voted for war (on April 25th). The cause was, they echoed, punishing Spain and giving Cuba independence.
The war lasted less than four months; Spain signed an armistice on August 12th after the Spanish navy had been defeated and largely destroyed in both the Carribean and the Philippines. Its final flotilla - guarding the coast of Spain itself against a feared American attack - never saw battle.
There was also land fighting in both the Philippines and Cuba, with both American troops and local rebels who welcomed American intervention, but - for all the fabled glory of the Charge of the Rough Riders in Cuba - the naval campaign was the most significant.
With the peace, Cuba was given its independence, as Congress had promised when declaring war. The United States forced Cuba into indefinitely leasing Guantanamo Bay Naval Base (which is still American-controlled today despite technical Cuban sovereignty), and giving American supervision over its finances and public sanitation (the sanitation was handled well and finances poorly; both provisions were rescinded in 1934), but they were independent.
However, Puerto Rico and the Philippines became colonies of the United States - and forced the United States to a public reckoning about having colonies.
They weren't, of course, the first territories the United States had owned.
But so far, essentially all the territories had been understood to be on the path to statehood. That'd been established by the Northwest Ordinance of 1784: all people in the territory (except the self-governing Indian tribes) were immediately given constitutional rights, and they were promised statehood as soon as a part of the territory had enough people and had written a state constitution for itself. That principle stayed through the Louisiana Purchase and further annexations. Even the Alaskan purchase, with little hope of settlement or statehood, had promised immediate constitutional rights.
But, Puerto Rico and the Philippines easily had enough population for immediate statehood. Still, no one wanted or expected them to become states. The people there weren't Americans; they didn't value American traditions. And, they were Hispanic (in Puerto Rico) or Asian (in the Philippines)... which was, sadly, enough of a justification for many Americans.
Instead, the objective was to annex them and govern them as perpetual territories: as colonies. On the one hand, this would project American power and build up American trade. On the other hand, this would supposedly give the colonies "the blessings of good and stable government", as President McKinley put it in his proclamation annexing the Philippines.
This "good and stable government" wouldn't necessarily be the same law as in America itself. The Supreme Court, three years later in 1901, confirmed that in the "Insular Cases". They invented out of thin air the concept of "unincorporated territories" where Congress or local authorities could govern without regard to the Constitution if they chose. And, for a while, they did so choose.
In the Philippines, there had already been a rebellion against the Spanish. Under President Emilio Aguinaldo, they'd joined with the Americans in the war.
Now, with the American annexation, they turned to become a revolution against the Americans. They had elected a Congress and President of their own (in fall 1898); they wanted to be free and independent. Their Declaration of Independence had consciously echoed the American Declaration of Independence. But instead, the Philippine–American War was a bloody and hotly-fought guerilla war, killing many times more and lasting much longer than the Spanish-American War itself. It started in February 1899; it gradually petered out through 1901, 1902, or even 1913.
Many Americans fought this, arguing - in the words of the newly-founded American Anti-Imperialist League - colonial ambitions were "inconsistent with the principles of this Republic", and "fraught with moral and physical evils to our people". As the United States Declaration of Independence said, governments derive their just powers from the consent of the governed - so shouldn't that be the case for the Philippines as well? Among the prominent members of this League were former President Grover Cleveland, industrialist Andrew Carnegie, and author Mark Twain.
A strong national debate erupted. In the Presidential election of 1900, incumbent William McKinley (with running mate Theodore Roosevelt who had become a celebrity leading the "Rough Riders" in Cuba) faced off against avowed anti-imperialist William Jennings Bryan who explicitly compared American imperialism to British rule over America.
However, imperialism got perhaps outweighed by another issue: the gold standard, which had huge implications for industry and finance. Bryan lost. Shortly after, President McKinley would be assassinated (for completely unrelated reasons), and Vice-President Theodore Roosevelt would lead the United States in even more imperial interventions.
The Spanish-American War was "a splendid little war", as the American Ambassador to Britain put it, but one with momentous consequences. It brought America into world affairs as, if not yet the acknowledged equal of the Great Powers, still a respected partner. Roosevelt's slogan would be to "speak softly and carry a big stick"; the Spanish-American War was what let America hold that "big stick" and made sure the rest of the world could see how big it was.
Sadly, it also pushed America down a path "inconsistent with the principles of this Republic."
To a large extent, we turned back from that path afterwards. Most treaty provisions in Cuba were rescinded in 1934; the Philippines received an elected legislature in 1916 and became independent in 1946. Puerto Rico got US citizenship and an elected legislature in 1917; they're still a US territory but have refused independence when it's been on the ballot.
But America has kept that worldwide influence, and even expanded it. Sometimes it's been used for good, sometimes for ill; and Americans debate which is which, and that is a continuation of the same debate that dated back to just after the Spanish-American War.
Roosevelt's saying looks remarkably like a paraphrase of a motto of the Society of Jesus: suaviter in modo, fortiter in re. I wonder if there might have been influence?