Based on the "Mars Attacks" cards... ( [link]
In a world not too dissimilar to our own, where China did not go Red (although Cuba still did), any chance of a Cuban Crisis taking place was averted when the Martians invaded in the spring of ’62. They really needed to, after all: a new technology gone wrong had led to an irreversible chain reaction within the planetary interior, and would before long crack Mars in half. If Earth was too hot, humid and heavy in gravity to be pleasant, the rest of the solar system was worse.
So the Martians invaded, with their saucers, their disintegrator rays, their force rays, their energy-draining or “freeze” rays, their giant robots, and their hordes of fast-reproducing genetically engineered war-bugs. It was unfortunate about the humans, but a reasonable space would be set aside for reservations for them.
Unfortunately, the humans were rather excessively attached to their planet, and when guns and bombs didn’t do the trick, moved to use atomic weapons with a lavishness that astonished the Martians. Still, the Martians plugged away, and probably would have eventually won, except that the reaction within the interior of Mars sped up unexpectedly, and Mars blew into three large and a great many small chunks while much of the Earth was still unconquered, leaving the Martian forces with a huge number of refugees often with no more than the shining metallic diapers on their hips, and a terrible supply problem: Martian Von Neumann machines were doing the best they could, but between human attacks and lack of easily accessed raw materials, local manufacturing of more weapons, giant robots, etc. was well below specs. The giant bugs were still merrily multiplying away, but they could hardly win the war on their own. They could still just blow up the planet, but they needed it for themselves.
So – the armistice of ’63. Martians withdrew from the major nations still in the fight, and later further concentrated their forces by withdrawing from tropical and/or densely populated lands more trouble to govern than they were worth. Both sides set to preparing for the next round.
50 years on, neither side has really gained a true advantage. The humans have duplicated few of the Martians superior technologies, but have gained the capacity to rapidly make the planet radioactively uninhabitable for either side: the Martians, on the other hand, have yet to find an adequate mind-control device or doomsday virus that will act fast enough and widely enough to Kill All Humans. Not that the Martians are all that evil: after all, they had not had war for many millennia on their home planet. However, they are rational and don’t tend to suffer from the Pathetic Fallacy: if it’s Them or Us, they will always choose Us, and fifty years of study haven’t improved their opinions on human rationality and common sense. (A lot of atrocity stories came out of the war, but really, drop a raw recruit with a death ray and no combat experience in an uncomfortable exoskeleton on an alien planet, with air often too dense and hot and humid to breathe, under 2.5 gravities, full of aggressive and hideous aliens who want to kill him any way they can, and see if a lot of trigger-happiness doesn’t take place).
Martians are thin, skeletal-faced and have corrugated cranial armor which looks uncomfortably like brains. They come in two sexes, which humans (much to Martian annoyance) cannot tell apart. They have a jolly sense of humor, most of which is untranslatable, which leads to really creepy laughter. From a cold, dry planet, they dislike greatly the hotter, more humid areas of the world, and voluntarily withdrew from much of the tropics. From a planet with a thin atmosphere, air at less than one mile of elevation tends to make them pass out from oxygen narcosis. From a planet with a lower gravity, they tend to use antigravity platforms and robotic exoskeletons to get around.
Or, at least they used to: thanks to Martian bioengineering, the latest generation of Martians, if still more fragile than humans, can get around unassisted in Earth gravity, although the current concentration of Martians at altitude means they are – as yet – not breeding for tolerance of the dense atmosphere of the lowlands. (Besides, Martians have their own kind of macho, and the little air-thinning mask is something of a mark of the Valiant Pioneer).
The Martian held onto the Sahara, too hot, and the Antarctic, with too much ice for their tastes, since they provided enough desolation to carry out induced-vulcanism Deep Mantle mining techniques without covering human cities with schmutz. The Emperor Penguin has suffered badly.
Much to the annoyance of the humans, Martians have largely cleared huge areas of their domains – especially ones with interesting mineral deposits – and moved them into “Human Concentration” areas. Unlike, say, South Africans, Martians have little need for cheap labor – robots and engineered animals do the grunt work – and prefer to have violent, unreasonably strong humans well away from where they live. Provided by the Martians with free electricity from their “lukewarm fusion” plants and free synthetic food, and in some cases piped-in water, the Human Concentration zones are left free to govern themselves and conduct business as they see fit, as long as they don’t develop arsenals of anti-Martian weapons: Martian presence is usually in the form of robotic spy-eyes. Conditions vary from nearly modern to abysmal, governments from democratic to despotic: emigration to the free or neutral nations is encouraged.
Most of independent humanity is part of the Union of Nations, a loose world government arising out of the old UN. It is dominated by the Big Five industrial/military powers: the USSR finally went at least semi-democratic in the late 1990s, the common Martian menace providing something of a unifying glue between its many peoples, while those Europeans not under Martian or Soviet control have unified into a federal state roughly as closely joined as OTL Canada. With Unity of Humanity being the order of the day, a lot of wee little bits of real estate never became independent, while much of post-Martian Africa is still essentially run by the UN. As the Union central government gained some genuine power, the World Assembly was moved from New York to Drogheda in Ireland, since nobody was particularly annoyed at the Irish (well, aside from the Protestant Irish).
Aside from neutrals, a few particularly poor and messed-up nations have become out-and-out Martian puppets, which provides the Martians with some useful “ins” to free human society. The most prominent of these is the one containing the Islamic holy cities: given Islamic sensitivities, this one has to be treated with kid gloves, but things have gone fairly smoothly since the leading clerical figures got their mind-control chips without anyone – least of all themselves – finding out about it.
Liberated not by the armies of Free Humanity but by Martian horror of heat and humidity, the nations of the Southeast Asian Block are quite anti-Martian, but refuse to submit themselves to the leadership of a so-called world government largely run by three white nations and the Japanese (they also don’t particularly like the Chinese, who try to use their overseas Diasporah as an entry lever to the local economies): they follow their own course, and have started to build their own Orion spacecraft.
(An unnecessary cost, in fact: at a UN research lab in Kazakhstan, Martian antigravity propulsion has been duplicated for the first time).