The other day, I was remembering the time when I read Mick Farren's SF novel Protectorate (1985). One scene that has stuck with me was one that showed us the thought processes of the "Protector," basically the ruler of the bulk of what remains of human civilization (long after an alien conquest), regarding an ugly decision. The Protector has become painfully aware that, because of some recent disturbances in one district of the city (the only city left!), he must have his military commander take out the troops to kill many of their fellow human beings . . . because the Protector is very much a puppet ruler for the alien occupiers ("the Wasps"), and if he doesn't kill a bunch of troublemakers, then the Wasps may very well use Weapons of Mass Destruction to kill a great many more humans -- or all of us at once, if they perceive us as too rebellious to be worth the headache of keeping around any longer.
That's a really nasty position for anyone to be in, and it made me wonder just when was the first time that a science fiction writer wrote something in which human defenders had not beaten the alien invaders, nor even fought them to a draw and then negotiated a truce, but instead had surrendered to them . . . and the alien regime had then demonstrated serious staying power, instead of being overthrown a short time later?
In other words: What was the first science fiction story that showed aliens successfully conquering the Earth in a reasonably "modern" or "futuristic" setting?
Note: If the actual story begins long after the act of conquest has already occurred, with the main characters living in a world where alien dominion is taken for granted as the current Status Quo, that still qualifies for my purposes!
"A modern setting" may be defined (for my purposes) as "when the aliens arrive, human science and technology has at least gotten started on what we now call the Industrial Revolution." That puts the earliest possible date for the alien invasion as being around the later decades of the Eighteenth Century (or in some alternate history where a similar level of technology exists at the moment when the aliens arrive and take over).
"A futuristic setting" may be defined as "human technology, at the time of the alien invasion, is significantly ahead of anything we have yet achieved in the real world." (Right now, I'm not interested in a story about a postapocalyptic future where, after a nuclear war or other devastating event, most surviving humans have reverted back to Stone Age conditions (or even Medieval ones) and then an alien invasion shows up to make things even tougher for us!)
"Successful planetary conquest" may be defined as: "For a period of at least five years, the alien occupation force undeniably was in control of anything on this planet that was really worth controlling, and the vast majority of the surviving members of the human race were meekly accepting orders from their new masters. These humans might not be happy about doing it, but they recognized that this was, in fact, the new government."
In such situations, the aliens didn't necessarily know or care about every single case where small groups of "free humans" were still living out in the woods, or deep underground, or whatever, but they had a tight grip on the cities, the heavy industry, the oil wells, the major mining operations, etc. That's enough to let me call it a real conquest.
Examples of What I Do Not Want:
Stories in which the aliens invade the Earth, trying to conquer it, and get off to a good strong start . . . but fairly soon (i.e., before the aliens have actually been running the show for five years at a stretch), the tables have been turned by human courage and ingenuity. Or even by dumb luck! (An early example was The War of the Worlds by H.G. Wells, and it was definitely "dumb luck" that saved humanity's bacon in that one.)
Stories in which the aliens only conquer a human colony on some other planet, but never manage to conquer Earth itself. (As an example of what this rule excludes: In Larry Niven's "Known Space" universe, the colony world of Wunderland was successfully invaded and subjugated by the Kzinti for many years during the first Man-Kzin war, although the rest of the human race eventually managed to liberate it.)
Stories in which the aliens are revealed to have once "conquered" the Earth, or as much of it as they felt the need to occupy, well before the Industrial Revolution ever got going. Perhaps thousands, or even millions, of years ago, and thus there was never a serious chance of terrestrial natives managing to muster the military resources to fight off a heavily-armed invasion force. (Julian May's "Saga of the Pliocene Exile" series, with most of it set six million years ago, in and around the area we now call "Europe" and "the Mediterranean Basin," qualifies as a prime example of what is excluded by this rule. So do any stories which have Stone Age or Bronze Age humans being subjugated by high-tech aliens who pass themselves off as a pantheon of mythological deities.)
Stories in which the aliens simply succeeded in their goal of exterminating the human race -- or at least all of us who lived on Earth at that time (regardless of whether or not they care about any stragglers in interstellar spacecraft or whatever). In other words, the aliens didn't even try to just kill enough of us humans to make the rest beg for mercy; they didn't have any mercy in the first place, and had zero interest in conquering us and turning us into slave labor! (Poul Anderson's novel After Doomsday deals with the aftermath of such genocide, with the surviving humans feeling very angry about what happened to everyone they'd left behind on Earth.)
Stories in which the human race had already died off (or very nearly -- perhaps a tiny fraction of the species still endured somewhere on or near the Earth) before the aliens in question ever came along and started surveying the planet. If the extinction (or near-extinction) of the human race was not the fault of the alien newcomers, then "conquest" is not the word I would use if the aliens decided they wanted to "colonize" all this lovely real estate which nobody else was using at the moment! (A.E. van Vogt's classic story "The Monster" presented a scenario where the human race was already extinct because of a catastrophic natural event before the alien viewpoint characters showed up . . . but the aliens made the fatal mistake of using their advanced technology to bring just a few humans back to life for interrogation, and then things got out of control . . .)
Got any suggestions? I don't care if the story you nominate is a full-length novel, or was a short story first published in a Golden Age magazine, or was an old movie, or even a comic book story, for that matter. I don't care if it's become famous as a "classic" science fiction story which is still in print today. I only care if it was chronologically the first piece of SF to look at the aftermath of a successful alien conquest of Planet Earth . . . "success," as I said above, being measured by whether or not the alien regime lasted for at least five years after it was established here!