Inspired by the Humans are Weird thread, with the idea that Earth is an unusually deadly (active plate tectonics, radical axial tilt, etc) world, and earth species are ridiculously tough and adaptable compared to most aliens.
Add the idea that most aliens are pretty pacifistic, taken from Alan Dean Foster's "Damned" trilogy.
Then steal from Harry Turtledove's Worldwar series, with the idea that one of the not completely pacifistic aliens gets in their head to invade Earth in 1944 and things go poorly for them.
The PCs are ordinary soldiers who become special forces who eventually go around invading alien space ships and fighting Nazis.
Why Invade a Death World?Edit
Most alien races can't develop properly in zero-G, low gravity, centrifugal gravity, or artificial gravity. So even highly marginal death worlds are valuable real estate if they have 1G. Heck, the aliens would colonize Venus if they could.
- Session 0 "Disaster"
- Alien gravtroops descend on Allied training bases. Chaos ensues. PCs die a lot.
- Session 1 "Opportunity"
- Weeks later, an alien cruiser is somehow brought down by Allied air forces. Now local Allied ground troops must fight their way to the wrecked craft and seize it. PCs die a lot.
- Session 2 "The Gate"
- Months later, human ingenuity has developed a way to use the alien craft's engines to teleport small teams up to 5 miles away. Trained special forces (ie, the PC survivors of the previous two sessions) are to be teleported onto low flying alien cruisers with instructions to seize them if possible or destroy them if not. PCs do that.
- Sessions 3+
- PCs engage in shenanigans on alien spacecraft, rescue prisoners, etc etc etc. The Nazis are probably cutting deals with the enemy, so go shoot their ambassadors and play cat-and-mouse games with SS-Jagdverbande operatives sent to steal alien technology during the peace talks.
Any attack that would kill or seriously harm a PC can retroactively be transferred to any other nearby NPC squadmate, killing them instead of harming the PC. This doesn't necessarily have to make sense. Grenades should be resolved by targeting the PCs first and then any surviving squadmate.
Even so, casualties should be pretty high. Sort of.
Typical Pacifist AlienEdit
There's a lot of alien races out there. This template is typical of most of them. Compared to a human, they're much more empathetic but amazingly easier to kill. They often have advanced technology that they use in very basic ways, which leads to really weird designs (ie, advanced computers but no robots/killer drones, advanced material science but starcraft still made from steel).
HP 8, HT 8, Empathy, Combat Paralysis, G-Intolerance, Hidebound, Low Pain Threshold, Pacifism: Cannot Kill, Temperature Intolerance (25 degrees), Unfit. Susceptible to extreme environmental elements is common, too.
The bad guys of the setting, these guys have a capacity for violence that only makes them really bad at it. Notably, they can engage in spaceship to spaceship combat, manage aerospace fighting, and perform aerial bombings without going around the bend. Their infantry forces are pretty terrible, but being able to carpet bomb the pacifist aliens mean that the aggressor aliens can have an expansionist space exploration policy with relatively low consequences. Until they get to Earth, that is.
They're also relatively innovative, which means that they can respond to a problem within a couple of years of encountering it.
As the game progresses and Allied technology gets ever better, these guys become less of a threat and the real danger becomes Nazis with alien technology.
HP 8, HT 8, Sensitive, Dull, G-Intolerance, Low Pain Threshold, Pacifism: Reluctant Killer, Temperature Intolerance (25 degrees), Unfit. Elite infantry units have a fair proportion of aliens that have bought off Reluctant Killer and can shoot people in the face without berating themselves for most of two weeks.
Pacifist aliens consider the aggressor aliens to be deadly wolves. Pacifist aliens consider human soldiers to be incomprehensible psychopaths.
- Fighting the Aggressors
Humans quickly learn that they want to close with the aliens as much as possible: At a distance, the aggressors can use artillery and grenades to kill humans, and alien artillery and grenades (TL9+ plasma thingies) is murderously effective. As soon as humans are inside the minimum range of alien grenades, it's all aimed shooting on the human side and hilariously ineffective flinching on the alien side. The aggressor aliens probably have some ultra-tech knockout grenades that could in theory be used at point blank range, but they're calibrated for use against pacifist aliens (and aren't very effective against a human in a gas mask) and it isn't doctrine to use them anyway, so the aggressors don't use them very often.
Japanese ground forces are surprisingly effective against aggressor aliens on a tactical level. Aliens have ultratech gizmos that can pick up infiltrating humans, but the Japanese are perfectly willing to go through terrible terrain that the aggressor aliens consider completely impassable. And a banzai charge is fairly effective against the aggressor aliens. Japan's logistical problems haven't gotten any easier, though, and the Japanese Imperial government is temperamentally unsuited to negotiating with aliens.
While humans can struggle against aggressor ground forces without doing horribly, the aerospace front is all in the alien's favor. Although some human aircraft can barely intercept some alien spacecraft, 20mm cannon and primitive rockets are too easily intercepted by the alien's anti-collision lasers. The alien's biggest weakness is lack of coverage: they can go anywhere and bomb almost any location on earth, but they don't have enough forces to cover everywhere they have ground troops so human bombers can make bombing runs when alien air cover is absent. Since the aggressors have never fought anyone with an effective air force before, it's taking them a long time to figure out how to suppress the human air forces and use air defense artillery when their spacecraft can't be present.
- Alien Technology
Aggressors are TL9 to TL11, with superscience elements, as appropriate. Their Dull nature means that they don't full exploit their infrequent technology advantages, so it's perfectly sensible for them to be wielding blasters but armoring themselves with kevlar or less. Probably a lot less - they should be vulnerable to tommy guns, because shooting aliens with tommy guns is cool.
Primary infantry weapons are Blaster Rifles, which are murderously overkill but why not? (note: not Pulsar weapons, which are even more dangerous but are explosive and therefore a huge hassle in play, so that's why not Pulsar). Dedicated grenadiers carry electromag grenade launchers with TL10 HEC grenades (8d+8 cr ex) or TL10 HEMP grenades (6dx5 (10) + 4d cr ex [2d]) (or optional biochem aerosols filled with weak (HT-4) sleep gas. Body armor is DR6 arachnoweave BDUs.
Aggressor aliens don't expect to be shot at in ship to ship combat, so their ships are surprisingly flimsy. They themselves are terrible at surviving crashes (the kind of car wreck that puts an average ST10 human in the hospital at -8 HP kills 50% of the aggressors outright and leaves another 25% mortally wounded) so while they do put escape pods on their ships, they don't put many of them and they tend to be badly located. Some of their larger ships can probably pull 1.5Gs but are unstreamlined, for an airspeed around 350 mph - just slower than the maximum speed of most late war fighters. Of course, even minimal TL10 point defense can handle any kind of rocket a 1944 fighter can toss out. And actual alien fighters that are streamlined and pulling 2Gs fly at Mach 5+.
The aggressors have fusion and anti-matter technology, but it never occurred to them to create fission, fusion, or anti-matter bombs. So while they're perfectly happy to use metallic hydrogen conventional explosives to level human cities, they can't just atomize the human resistance. And sustained carpet bombing doesn't work particularly better for the aliens than it does for the Allies in WWII: it's really, really hard to knock out a factory permanently.
- Alien Doctrine
The aggressor's long established method of securing new habitable worlds was to send scout ships out from an established colony. When the scout ships found a habitable world, a battle fleet was sent to seize it. Any existing native population was bombed from on high until it surrendered. Ground troops were used to push the survivors into reservations in the less hospitable parts of the planet. The survivors were then allowed to die off.
It would never occur to the aggressors to wait until the inhabitants of a planet they wanted were fighting among themselves, because that never happened. Their arrival during WWII is just unfortunate coincidence.
- Alien Doctrine and Earth
The aggressors are very confused by Earth; humanity is already thriving in parts of the world where the aggressors intended to resettle them. They know how to deal with enemy aircraft and spacecraft; they don't know how to deal with enemy fighters that attack their spacecraft. Most of their ground troops are really military police; they can damage (most) human armored vehicles with their sidearms or destroy them with HEMP grenades but they don't really have a tactical doctrine to resist a tank rush.