Proposed story by Sir Fragsalot (bssrpantella@hotmail.com)

It is the year 2025. Six years ago, you and 1300 other people were selected
by the International Space Administration (ISA) to create the first Jovian
colony on the moon of Europa. Among the people selected for the Europa
Colonial Expedition (ECE) were scientists, botanists, geologists, a few
politicians, farmers, and all the other professions that would be needed to
create a self-sufficient colony, and, in time, completely terraform the
surface of Europa. You were one of the single Army platoon sent to Europa to
keep law and order among the colonists. If ISA had any idea of what your job
would actually become on Europa, they wouldn't have launched a rocket there.
They would have launched a nuclear warhead...

The first two years on Europa were easy. All you had to do was help set up
the colony: haul equipment and assist the in the construction of the
buildings. Once the colony was built, policing it couldn't have been easier:
the people selected for the colony were, by definition, respective of their
fellow man. Everything seemed to be going smoothly. The nuclear power plant
used during the initial construction of the colony was decommissioned, as a
power plant using harnessing the heat of Europa's core was built. The
terraforming project was off to an incredible start. Parts of Europa's
surface already looked just like Earth's, and humans could live, unprotected,
in those parts. But then the geologists started mining deeper into the moon.

Almost at once, the mining expeditions were in trouble. Equipment was lost,
vehicles were damaged, and a few miners lost their lives. Your Army platoon
ended up performing many rescue operations. Half of your platoon died on the
rescue missions from the brutal Europa environment.

If only the environment had been to blame for the mining incidents. Multiple
races of beings began appearing, coming from the dark caverns within Europa.
Caverns filled with the requirements for life: light, heat, and food.
Europa's molten core and oxygenated atmosphere, the reasons that ISA
originally selected the moon for colonization, created the greatest
opposition to the colony: alien races who brutally defended their moon. Some
of the aliens were humanoid in appearance, but some looked completely
different than any life seen before by human eyes. And all moved with a
single deadly purpose.

At first, the colonists were thrilled to have discovered alien life within
the solar system. But immediately after the discovery of the alien races, it
became clear that they were behind the failure of the mining projects. Soon
the aliens began attacking the colony itself. ISA couldn't be communicated
with, as the aliens attacked and destroyed the communications array before
any information about the discovery of their existence could be relayed.
Building after building was overrun by the aliens, who added their own rooms
and symbols to the Earthly architecture, turning parts of the colony into an
other-worldly architectural nightmare. Your platoon, sent for police duty,
became the sole hope and protector of the colonists. As the colony was taken
over, you and your squad mates defended the colonists as they evacuated each
part of the colony, suffering many casualties. The alien races were
intelligent, carefully selecting which parts of the colony were weakest and
attacking those first. The soldiers who lost their lives defending the colony
had their weapons scavenged by the aliens and used against the other
colonists.

And then the shuttle bay was overrun. Cut off from escape, your platoon, now
reduced to the size of a squadron, created a fortress in the one remaining
building. Faced with the potential death of every colonist from starvation,
your squadron drew straws to decide who would venture out from the fortress
in a hopeless quest to retake the shuttle bay before the aliens could
discover how to use the shuttles and bring their forces against Earth. Your
squadron could spare only one man, as twelve soldiers were all that remained,
and as many as possible were needed to defend the colonists.

You drew the short straw. Leaving the fortress, you take only a pistol, as
the eleven soldiers left to defend the colonists need all of the other
weapons to hold off the aliens for as long as possible. The hopes of the
colonists, and, all of Earth's inhabitants, rest entirely upon you.