ExForce-One

The year is 2120 and Terra has been attacked. Humanity has met an alien species, and those aliens have tried to remove humanity from the universe. They attacked without warning, without mercy - only desperate measures saved the world from their attack, but vast swathes of land have been devastated by the crashing spacecraft and nuclear fallout.

But humanity is not about to curl up and die - a global alliance has been created that has ruthlessly united the fractured nations of humanity. Alien technology has been forced to serve its victims. Armies have been formed, spaceships have been built, and the Coalition of Allied Nations has sent forth the 1st Expeditionary Force to confront the aliens outside Terra's solar system and exact revenge for humanity's losses.

In 2120 three alien spacecraft appeared in the solar system above Terra's elliptic, roughly 30 AU from the sun (that's the distance of Neptune's orbit, by the way). One ship vanished within hours, but the other two proceeded towards Terra at a tiny percentage of lightspeed - still fast enough to cover the vast distance within a dozen days. The asteroid defense systems detected the spacecraft but were utterly incapable of dealing with objects moving at such tremendous speeds.

The aliens made no attempts to communicate. Their ships crossed into the asteroid belt, destroying any human installations and craft encountered. Their first contact with Terra itself was through artificially propelled asteroids sent as kinetic weapons against the planet. The asteroid defenses were able to reduce much of the damage, but the devastation was still considerable. Immediately following the asteroids were the spacecraft themselves, closing on Terra and lancing the surface with powerful weaponry fired from orbit.

Humanity responded with experimental fusion-warhead-tipped missiles fired from secret military installations on Luna and military satellites in orbit. The weaponry forced the alien spacecraft into Terra's atmosphere, where surface-launched missiles and anti-missile defenses bombarded them. The ferocious assault damaged the spacecraft enough to cause them to crash - one slamming into Mexico and the other plowing through eastern Europe and western Asia. The damage was immense.

Over the next years humanity scavenged the alien ships and prepared for war. The United States and the Republic of China led the way as the world's two dominant superpowers - a new global government was formed. Every nation joined, one way or another. Faced with a little known alien threat and the very real possibility of extinction, no dissenters were allowed. Terra exists under martial law and years of wartime economy as every spare resource is put to creating defenses and military forces. Any nation, any individual, that does not get onboard is subjugated or eliminated.

The new world government, christened the Coalition of Allied Nations, has created the Coalition Military Command. Ten years after the first alien attack, CAN-CMC has sent out the first Expeditionary Force (ExForce). ExForce-One's purpose is to take the fight to the aliens and keep it there. Cause as much destruction as possible, explore as much as possible, and above all else, keep the aliens too occupied to attack Terra again.

Campaign Idea

Characters are members of the front wave of the Earth assault force,
taking the fight to the enemy. Unbeknown to them, they are considered
somewhat expendable, since one of their primary purposes is to keep
the aliens occupied away from Earth, since Earth can't afford to
suffer another attack like the previous one.

Probably playing some form of assault force doing ground attacks on
alien planets, equipped with military battle suits. Part of a small
fleet, maybe two or three ships. The ships would likely be fairly
cobbled and rushed, a lot of the technology untested, so plenty of
problems there.

Thoughts

Are there aliens left alive on Earth? Guerrilla warfare on our own
planet?

How long until the aliens come back?

How does Earth know that the aliens are hostile and want the
extermination of the planet?

How does the alliance know where the aliens are to take the battle to
them?

What about Earth's civilization? How is Earth affected and what
nations are on board and which ones have to be brought on board
forcefully?

What type of battle would the advance force be dealing with? Space and surface.

Wormhole Nexus - There is a network of spacial anomalies that connect star systems. Creating certain energy fields allows for transportation along these pathways nearly instantaneously. Not a natural phenomena. Some pathways are more stable than others. Some allow larger payloads.

Alien Ideas

Do the aliens have FTL communications? What are the capabilities of
the aliens?

What is the alien psychology? Are they genocidal, unable to accept the
existence of any other species? Religion and society?

What is the general make up of the alien race? How similar are they
to humanity, where are they from, how did they get here?

How much do the aliens know about humanity?

Truly alien beings who have made no attempt to contact or deal with humanity. Don't think like humans. Humans able to derive some of their technology, but just barely. Openly genocidal - no other species is allowed to exist, any race detected is immediately set upon.

Where are the aliens from?

Technology Ideas

Battle suits – Technology should be advanced enough to allow for
military grade exoskeletons that enhance human soldiers.

What kind of technology is scavenged from the remains of the alien
ship(s)?

Could you make spaceships out of Pykecrete? 86% water frozen with 14% wood pulp, sealed within an insulating layer, continuously refrigerated through tubes run through the ice. Much stronger than conventional ice - but how strong?

Deploy unmanned strikecraft similar to Predators or scale-model airplanes? Dropped through atmosphere in disposable sheathes to prevent burn up. How are they retrieved? How do they produce more launch sheathes?

Would the advance ships have certain production facilities onboard due to the lack of supply lines? Supply would take much longer than surface navy ships, even with FTL and high-speed drives.

Speed notes: Aliens appear @ near-Neptune orbit, above elliptic. 30 AU from Terra. 1 AU = 150 mil km. 30 AU = 4.5 bil km. Cover 30 AU in 12 days (288 hours) = 15.6 mil km/hr. Speed of Light = ~1.079 bil km/hr. Alien ships travel at roughly 1.45% lightspeed.