After a successful initial tour as a Marine rifleman, Lance Corporal Gracie Medicine Crow volunteers to become a scout-sniper, one of the deadliest - and most dangerous - military specialties in the United Federation Marine Corps. Gracie comes from the Apsáalooke Nation, a people with a long history of military tradition. Small in stature and considered stunningly beautiful, she is often underestimated, but that merely drives her to be the best sniper in the Corps.

United Federation Marine Lance Corporal Tamara Veal catches the attention of recruiters who nominate her to serve as a Single Combat Specialist. Gladiators, as they are better known, are genetically modified human champions who meet Klethos d'relle in the combat ring when the Klethos issue a challenge for a human world. Win, and the planet stays in human possession; lose, and not only do they lose their lives, but the world as well.

Esther and Noah Lysander are the twin children of General Ryck Lysander, Commandant of the Marine Corps, leader of the Evolution and Chairman of the Federation. When they are told that their father and mother have been assassinated, they are both devastated. Cut adrift, they each decide to enlist in the Corps - but for different reasons.

They've lived in orbit around planet Lumus for centuries and, for all they know, no one else exists but them. However, they don't know how their race got here. No history book has an answer and no historian has the guts to find out. It's as if the history of their race, the human race, originated in orbit around this planet. Any knowledge of their distant past has either been erased or their Prime Director is correct - they were birthed here. They know of no enemy, no threat, no carnage, and because of this they aren't prepared for what's coming.

When the Earth Republic is savagely attacked, they recruit the universe’s most dangerous minds to retrieve their stolen warships. But as this ragtag group of criminals embarks on a suicide mission to fight for their lives and freedom, an even bigger threat emerges….

Human slavers attack. Despite trying to fight back, there is nothing the young Leefe can do to save his family and friends. But he doesn't have to. The Imperial Marines arrive in the nick of time, and they hate slavers. Three tri-years later, when the new emperor issues a proclamation to integrate the imperial military with non-human citizens, Leefe is among the first to volunteer. Integration to resurrect the empire as a force for good is challenged by centuries of prejudice against the "dung races." 

Cam Alvarez is a Drop-Trooper. A warrior-knight wrapped in the futuristic armor of a high-tech battlesuit, and he’s one of the best. When he’s promoted to sergeant and asked to become a leader, he faces a whole new challenge. The Marines are striking deep into enemy territory, and the casualties are mounting. Cam is torn, knowing his job is to follow orders and carry out the battle plan, even if he doesn’t agree with it. But his squad has become his family, and now he’s being asked to lead his family into battle, knowing it will mean their deaths. 

Ryck Lysander has proven himself as a Marine, as a warrior. As he is promoted to sergeant, though, his responsibilities expand beyond merely fighting to leading other Marines into battle. When an old ally becomes a new enemy, one well-equipped and trained, Ryck is pushed to his very limits as he tries to keep his Marines alive while fulfilling his mission of defeating the enemy on the field of battle.

Desperate to escape a life of poverty on his desolate home planet, Ryck Lysander enlists in the United Federation Marine Corps, hoping to make a better future for himself. However, Ryck soon discovers that the Corps is more than a means of escaping his former life as he is pushed beyond the very limits of his strength and willpower.

As a captain, Ryck Lysander is given one of the most sought-after billets in the marines: an infantry company commander. His new battalion commanding officer, however, is not impressed with Ryck's past accomplishments, and Ryck finds himself struggling to fulfill the CO's expectations. Used to his "hero" status within the corps, his new position of having to prove himself grates on him. Now, as his company marches to the sound of gunfire, Ryck must find it within himself to be an effective combat commander.

As a certified Federation "hero," Sergeant Ryck Lysander is offered a commission as a second lieutenant. Only, he doesn't feel like a hero, and his tendency to jump into a fight himself is at odds with his mission as a junior office. Accepting his commission might have been a big mistake. When contact with an alien species is finally made, that contact is not peaceful, and Ryck is thrust back into combat, combat that does not end well and plunges Ryck into an emotional crisis.

Esther Lysander, the driven, professional Marine ever-conscious of the heavy weight of her father's legacy, is selected to become an officer. She has high goals for her career - very high goals - and she believes the best method to achieve success is to be a complete hard-ass, keeping emotions at bay. This outlook has resulted in some notable achievements, but at the cost of friends and her relationship with her twin brother Noah, a price she is willing to pay.

Jasper van Ruiker is an elderly algae farmer, drafted into the local militia to defend his village from the invading Tenners. Lieutenant Castor "Mountie" Klocek is a Navy pilot, shot down during an air-to-ground mission. Lance Corporal Javier Julio Gregory Portillo and Sergeant Gary Go are Marine combat engineers, the only survivors of a deep-recon mission to destroy a bridge.

Major General Lysander has spent 38 years of his life dedicated to the Corps and sworn to perform the duties assigned to him by the Federation. In the process, he has become the most decorated Marine in its history. Ryck is faced with a situation that so horrifies him that he cannot accept it. Can he just stand by and let it proceed, or will he become an oathbreaker and put not only his life, but more importantly, that of his family, his fellow Marines and sailors, and the citizens of the Federation in peril?

The Corps has been integrated by imperial decree - but that doesn’t mean everyone accepts the wyntonan Marines. Despite an impressive combat record as a grunt, Corporal Leif Hollow struggles to become an effective NCO and leader of Marines. When the trumpets of war sound, however, Marines forget about differences and come together to accomplish the mission. But when the odds are stacked against them and the empire’s very existence is at stake, will that be enough?