After training as an ITO Special Forces candidate in ITO's training facility, your journey begins in the Interstellar Marines campaign. Below is just about 1/10 of the total storyline in the campaign.

First watch this trailer for the campaign:

Now watch the narrated story with visuals (spoilers are cut out):

Text version of story (spoilers are cut out and replaced with ...):
Since man first raised his head to the stars above, he's dreamed of conquering space. Interstellar Marines is the age-old dream come true.

It's the dawn of the twenty-second century, a time of great hopes and expectations. The discovery of a new and inexhaustible well of power, known as zero-point energy, has revolutionized space travel. Man has escaped the confines of Mother Earth and gone on to colonize the solar system.

But far away from public awareness an ambitious military project has already taken man beyond the final frontier and into the regions of the stars.

Employing the full potential of zero-point energy …

The powerful Interplanetary Treaty Organization, ITO, has secretly constructed the first human settlement in another solar system. The colony, on the distant and fertile planet Valhalla, is home to some 5,000 researchers and personnel. Among them, head of exterritorial research, Jack Torillo. In the forests of Valhalla, Jack Torillo and his research team has discovered … prior to the advent of man. But at the brink of the greatest discovery of his life, fate has it otherwise as Jack is …

None of this is known to four soldiers as they arrive at a military facility on the moon to complete their training as black ops within the ITO Special Forces.

On a seemingly routine mission to Mars, their combat readiness is immediately challenged as they become deeply entangled in an operation under Interstellar Marines jurisdiction, a division known only to a closed circle of high-ranking ITO officers.

In the aftermath of the mission, the players are now themselves reassigned to the Interstellar Marines. Lieutenant Reese, the man responsible for the reassignment, reveals that the Interstellar Marines was founded by Jack Torillo to protect humanity against the threat of a possible hostile alien encounter.

As the true scope of the purpose becomes clear to them, strange …

Less than twenty-four hours after enlistment, the players are sent on their first mission as Interstellar Marines.

ITO Strategic Command has lost all contact with the orbital research station Xeno-13, where scientists are developing lethal viruses as well as genetically engineered creatures for planetary warfare.

On route to Xeno-13, the mission is outlined by Lieutenant Reese. Priority one is to infiltrate and retrieve all vital research data. Priority two: eliminate anything standing in the way of priority one.

Inside the research station …

… from when Jack Torillo worked there, and how he and Lieutenant Reese are both engaged in a military …

After having been to hell and back, fighting the biological horrors of modern planetary warfare, the players are transported back to Interstellar Marines headquarters, to be lauded with medals of honor.

But calm is a short respite, as alarms erupt the ceremony, the complete lockdown of the ITO space development complex, located just below the main facility, are in progress.

The players are sent down to investigate along with two additional Interstellar Marines teams, and a military defense robot.

Almost immediately upon arrival underground …

The security AI has detected an unknown intruder coming through … aggressively defending against any attempts to reach the …

Alone, and disconnected from backup, the players have to bypass the automated defense system to … the AI.

When the players finally reach … they are met by a most horrific sight. A fierce … new prey.

Contact with the colony on Valhalla has been lost and the players are ordered to … and report top-side. They are to board an Interstellar Marines star cruiser, currently being prepped for an emergency mission to Valhalla. An alien encounter, for which the Interstellar Marines are the first line of defense, is finally a reality, just as Jack Torillo had anticipated. But to what extent only becomes clear as they arrive in orbit around Valhalla, the star cruisers …

While the 21st century saw Humanity's forays into space ebb and flow, the 22nd century was far more positive. Several key events contribute to an explosive growth in the space industry all around the globe.

In the latter half of the 21st century the world was experiencing a cautious economic upswing. Commercial interest in space was slowly rising, following the successful deployment of the joint Chinese-European lunar research bases. But it took the Japanese built and privately owned space station "Hotel Dawn" to fully jolt the European space businesses to life. Despite catering only to the ultra-wealthy, at the time it opens in 2080 the waiting list for a vacation in space are years long. It manages to operate at a profit, sending the budding aerospace industry skyrocketing. Companies from the western world soon lay plans for a settlement on the moon, catering to low gravity manufacturing, Helium-3 mining and tourism.
 

Mining operation on the moon

Meanwhile, the aging International Space Station, still in orbit after its abandonment in 2025, steps back onto the world stage. It is refitted and reopened in 2097 for the purpose of performing high energy experiments. Just a few short years later the team of scientists are successful beyond their wildest dreams, creating the worlds first Zero Point Energy reaction.

With limitless energy came an enormous growth curve in space exploration. The commercial sector went beyond exponential growth, with an increasing number of privately run orbital stations and lunar facilities under construction. More and more countries of Earth join with the ITO alliance, and under its guidance mining facilities are erected on Mars and even as far away as the asteroid belt.
 

A time of growth in the aerospace industry

The discovery of this virtually unlimited ressource was the beginning of a new era, and the union of human kind. Learn more about the first experiments that formed the foundation for interstellar travel.
 

Zero Point Energy reaction

Few believed that the exponential technological evolution of the 20th century would ever be paralleled. The 21st century not only paralleled it – it went beyond it. The single-most important reason for this was the discovery of Zero Point Energy.

Originally proposed by Albert Einstein and Otto Stern the concept of Zero Point Energy started as a purely theoretical quirk to explain a residual term needed to solve the equations of quantum mechanics. One April morning in 2100 aboard the International Space Station, a team of top scientists from all around the world managed to produce a quantum of energy from the vacuum of space surrounding them. Showing the possibility to generate pure energy exploiting the fabric of space-time itself, the experiment showed promise to solve the depletion of Earth’s energy sources. It was the end of a dark age of apocalyptic prophecies, and the beginning of a brighter and better future.

Experiment
It was suggested to diverge the power obtained in the experiment to the propulsion system of the space-station holding it in orbit. Rather than maintaining stationary distance to Earth as predicted, the experiment sent the 2 million ton space station hurling rapidly away from Earth threatening the lives of those aboard. An emergency rescue mission led by the ITO special forces managed to retrieve the ISS-scientists and most staff after almost 10 months of chasing the uncontrollable facility.

Subsequent evaluation of the experiment revealed it to have generated energy equivalent to roughly 86% of that produced by powerplants in the entirety of human history.

The Interplanetary Treaty Organisation, ITO, is an alliance of countries that wishes to further the exploration of space. To do so it provides a stable social and economical platform on Earth in order to nurture the commercial space sector. During its century long existence it has focused on expansion through the spreading of cultural and economic goods, specifically staying away from using its armed forces in anything but defense. Although diplomacy is its primary vector it maintains control over a formidable force of hardware and personnel.
 
As the 21st century drew to an end, Europe was experiencing an economic
boom. Its population ached for access to space, there was mounting pressure for faster, better, cheaper ways to get to orbit and the moon. The commercial aerospace industry had seen a huge increase in demand for materials brought to and from space, more and more satellites and high-tech manufacturing facilities were put up.

There was a small but growing space tourism industry coming to life, with a space station already in orbit catering to a rich clientele and a similar habitat under construction on the moon.

But a sense of worry was growing, that the economic boom would not last or that human stupidity would force us to abandon all space efforts again. Something needed to be done to ensure a stable base from which the expansion into space could continue. That materialized in 2096, when a proposed alliance was ratified by western European countries and the Interplanetary Treaty Organization was created. It's goal would be the pursuit of peaceful expansion, leveraging the combined economic resources and military might of its member countries.

To keep the territories stable ITO has been hard at work knitting together the populations of all these incredibly diverse cultures. While each nation retains their sovereignty, ITO has implemented a series of standards designed to allow the freedom of movement of people, goods and services across its nations. The same basic infrastructure and education is in place across all countries, creating a common foundation between the people. ITO also provides financial aid to countries to boost their standards of living and industrialization.

They've pushed especially hard on education, with ITO-run schools and universities being particularly prevalent in South America and the Middle East. In little over a century ITO has successfully eased much of the tension in what used to be the hotspots of the world. Its number of nations grew quickly: In a series of expansions taking place over sixty years, ITO spread from its original founding countries to the current list of over eighty countries. Amongst its members are almost all European and Middle Eastern countries, large parts of Asia, Russia, the United States of America, and most countries in Africa and South America.
 

ITO member nations

Especially noteworthy was the 3rd Expansion in 2121, where ITO dedicated their resources to financing the construction of Zero Point Energy reactors to all its member nations. The gift of limitless energy won many countries over that were previously thought impossible to persuade peacefully.
 

ITO multi-purpose vehicle on approach to a privately run spacestation

To this day ITO maintains direct control over all orbital traffic within its territory; no individual nations are allowed to operate aerospace vehicles without the use of ITO-trained pilots. Concern has been raised over this level of control and potential for abuse, but ITO maintains that a unified command and control structure is required to safely operate in space and ensure constant growth in the space industry. The ITO countries are responsible for almost 70% of all space-faring traffic (the remaining traffic is generated from the CoSEA territories)

ITO Organization
ITO is organized into the following political offices, scientific endeavors, civilian programs and military structures:
 

Divisions of ITO