War Criminal. Abner Fortis, ISMC, #11

The United Nations of Terra (UNT) will never forgive or forget the terrorist attack by the Kuiper Knights that killed over one hundred thousand Terrans. The Space Marines may have won the battle against the Kuiper Knights on LAM, but the war continues in the shadows. The Master is dead, but some of his top lieutenants evaded capture, and the UNT wants them to pay. To get revenge, UNT President Okoye signed the Swift Sword Protocol, which authorized the pursuit and assassination of certain fugitives. Major Abner Fortis is recruited by the new Intelligence, Surveillance, and Reconnaissance Agency (ISRA) for a Swift Sword mission.
When Master Gunnery Sergeant Petr Ystremski is sidelined by a terrible tragedy, Fortis is teamed up with his old friend and former Space Marine Jocko Bender to hunt down a short list of familiar names: Emil Zerec and JJ Zylstra. It's a dirty and dangerous mission. Zerec and Zylstra are skilled and ruthless, and they are supported by a shadowy network of sympathizers that the ISRA is only beginning to unravel.
Fortis and Bender chase the pair of Kuiper Knights from familiar stomping grounds to strange new worlds in order to deliver justice like only Space Marines can. When an unexpected opportunity arises and the scope of the mission changes, Fortis and Bender are called on to do what they do best: improvise, adapt, and overcome.