The early novels focus on the conflict between the US and the UN over the new technology. In later novels, the human race begins to encounter other intelligent species.
- Heritage Trilogy
- Semper Mars (1998)
- Luna Marine (1999)
- Europa Strike (2000)
- Legacy Trilogy
- Star Corps (2003)
- Battlespace (2006)
- Star Marines (2007)
- Inheritance Trilogy
- Star Strike (2008)
- Galactic Corps (2008)
- Semper Human (2009)
This series contains examples of:
- Absolute Xenophobe: The Xul are instinctually driven to wipe out any species that has even the tiniest possibility of developing into a threat to their galactic dominance. To this end, they hunt down any civilization advanced enough to broadcast into space and bomb the hell out of it with asteroids.
- Abusive Precursors: The An's only reason for coming to Earth in prehistoric times was to use humans as slave labor, and sometimes as food.
- Alternative Calendar: By the Inheritance trilogy, the Corps has become so much a self-contained culture that they've begun using their own Marine Era/Annum Manus calendar, with the months simply numbered and Year 1 being 1775, the year the USMC was founded.
- Ancient Astronauts: Three different aliens intervened in Earth's ancient history. First the cybernetic or mechanical Builders who tinkered with the ancient human genome to create Homo erectus, then the An who used human slaves in ancient Mesopotamia, and finally a third species who helped humans get back on their feet after the An were wiped out. Some of the conflict on Earth arises from the so-called "Ancient Astronaut" cults, who claim that aliens were benevolent gods, who will eventually return and solve all of the world's problems.
- And I Must Scream: Anyone patterned by the Xul suffers this. The Xul disassemble the victim atom by atom and download all of the information that defines them into their computer banks. The victim's consciousness, or at least a perfect copy of it, ends up stuck in the Xul's computers, being analyzed for information and eternally suffering the pain of their disintegration.
- Antimatter: In Luna Marine, the discoveries of Precursor ruins on Mars and the Moon kick off an Archaeological Arms Race between the US and the UN, using antimatter as a basis for space propulsion and weapons systems.
- Apocalypse How: The Xul attack on Earth is a high Class 1. They slam an asteroid into Earth, killing around four billion people and devastating the Earth's climate, but human civilization as a whole survives.
- Balkanize Me: Mentioned in Luna Marine, where the UN is desperately trying to hold together and force the rest of the world into One World Order. Unfortunately for them, the current tendency in the world is the opposite — splitting countries into smaller political entities. Interestingly, one of the reasons for the US-UN war is the attempt by the UN to force just such a thing in the US with the creation of Aztlan from the Southwestern (i.e. Hispanic-dominated) states.
- Big Bad: The Xul are the ultimate villains of all three trilogies. In the first, they're simply the looming "Hunters of the Dawn" responsible for interstellar genocides in the distant past, but they take center stage by the end of the second, and are the main antagonists of the third.
- Bizarre Sexual Dimorphism: Adult N'mah females are four-meter-long eel-people, fully sapient and very vaguely humanoid. The males, meanwhile, are mindless, meter-long worm-things that live within the females' reproductive tracts, serving only to fertilize eggs.
- Colony Drop:
- In Luna Marine, the UN attempts to do this with an asteroid in an attempt to cripple the US and end the war quickly. The author goes into great detail to describe the sheer destruction such an act would cause. The asteroid is destroyed, although the fragments do a fair amount of damage. The wreck of the ship steering the asteroid, though, falls on Chicago, killing around a million people and irradiating the city for several centuries.
- David Alexander finds video records of the Ahn colonies on Earth being wiped out by a tidal wave, caused by an asteroid dropped into the Red Sea by the so-called "Hunters of the Dawn".
- This is generally how the Xul, the Hunters of the Dawn, deal with species they consider a threat. Much of Star Marines revolves around a Xul attack on Earth and its aftermath. While Earth's forces manage to destroy the attacking huntership and nearly all of the asteroids it launches, what gets through is enough to cause a calamity on par with the K-T extinction, aptly named Armageddonfall.
- Easy Logistics: Averted in the first novel, where the marines on Mars explain that someone in supplies messed up royally, issuing them desert gear, apparently not reading the part of the sentence where it says it was a Martian desert. This includes desert boots, even though their sealed suits have no need for extra footwear. Their weapons also need to have their sights recalibrated, as they're set for the higher Earth gravity. To be fair, though, no one before thought that the Corps would send people to another planet. In fact, the government was seriously considering disbanding the Marine Corps.
- Expanded States of America: At the start of the series, the USA has annexed most of Canada, except for Quebec which became independent. By the end of the series, there are a total of 75 states.
- Good Adultery, Bad Adultery: In the Heritage Trilogy, Dr. David Alexander keeps having extramarital affairs with his female colleagues. It's stated that social mores have changed to the point where marriage isn't treated as something monolithic. Still, there are many holdouts from the more strict religions, who cling to the old marital traditions. Unfortunately for Alexander, his wife is one of them. He doesn't want to stay married to her and has brought up divorce multiple times, but she refuses to even contemplate it due to her very religious upbringing.
- Legend Fadesto Myth: A recurring theme of the series. Over the centuries, the details of events like Garroway's march are smoothed over. In Semper Human, the Xul attempt to use the full details of legendary events in the Corps history, like the Battle of Derna, as a psychological attack against the marines.
- Lizard Folk: The An, known to themselves as the Ahannu, are an alien example. They look more or less like humans, but with reptilian features and bulging eyes.
- Reality Warper: The Xul's manipulation of quantum wave functions makes them essentially this. They're far from omnipotent, but they can tinker with the inertia of anything close enough, making them near-invincible in space combat, and "download" objects and organisms right out of the universe.
- Space Marine: What the US Marines become over the course of the series. The early novels have a lot to say about how they adjust to novel conditions on other planets and in microgravity.
- Transplanted Humans: In Semper Mars, an expedition at Cydonia, Mars, discovers ruins half a million years old. An American archaeologist then discovers skeletons that appear to indicate that whoever had built the ruins also abducted Homo erectus from Earth and genetically modified them, possibly using them as labor to build the Face.
- Still-living examples are found much later, when the Marines reach Ishtar and find that the An/Ahannu still keep human slaves there.
- United Nations Is a Superpower: In Semper Mars, the UN has grown in power and influence to the point where it's almost a One World Order. Several nations (including the US, Japan, and Russia) still resist the UN's more and more forceful demands that they join the European-dominated organization. Halfway through the novel, the UN declares war on the "rogue" states over the findings on Mars.
- United Space of America: The United States are a major player in Earth's galactic future. The first trilogy describes why.
- Vicious Cycle: In Luna Marine, David Alexander comes up with a possible explanation for the Fermi paradox
, given the discovery that the galaxy is teeming with sentient life, and at least three alien races have set up colonies on Earth in the past. He speculates that star-faring races arise periodically and expand out into the galaxy every few thousand years or so. But, at their peak, they're discovered and wiped out by a predatory species, so-called "Hunters", whose mindset is "kill them before they kill us." Then, the Hunters usually destroy themselves through internal warfare or multiple Hunter races destroy one another. This clears the stage for another few millennia until another "generation" of races makes their way into space. David fears what may happen if new Hunters discover Earth before humans are ready to fight them, while his nephew speculates that humans may be the next Hunters. - World War Whatever: By the end of the Legacy Trilogy, Earth is up to World War VI, although only the UN War (World War IV) is directly important to the plot. World War III is implied to either have been The War on Terror or to have grown out of it.
- Zero-G Spot: In Semper Mars, Dr. David Alexander carries on an affair with his French observer during the long voyage between Earth and Mars. Finding room to do this in the cramped cycler is difficult but not impossible. They end up using harnesses to keep themselves from drifting away from each other during vigorous thrusts. There's also plenty of cleanup afterwards, trying to chase down all the fluid droplets before they get into some critical system. Apparently, there is also a space version of the Mile-High Club called the Three Dolphin Club. In Luna Marine, Alexander explains to his new lover that, when dolphins have sex, there is a frequently a third dolphin helping "push", hence the name.
