Jim Raynor was a Confederate marshal on Mar Sara at the time of the first zerg incursions on that world. Despite bravely fighting the alien aggressors and saving many lives, he was arrested by Confederacy forces on the pretext of destroying Confederate property at Backwater Station. When he was subsequently liberated by Arcturus Mengsk's Sons of Korhal, an anti-Confederate revolutionary group, Raynor chose to fight alongside them.
Mengsk's hunger for power and his growing lack of scruples soon began to trouble Raynor. Eventually Mengsk's betrayal of his own lieutenant Sarah Kerrigan and his ruthless manipulation of the zerg to attack Confederacy-held worlds showed Raynor that Mengsk was no better than the oppressors he sought to overthrow. Raynor led a revolt within the ranks of the Sons of Korhal and seized Mengsk's personal flagship, the Hyperion, and a small fleet of ships. While attempting to rescue Kerrigan from the zerg planet Char, Raynor encountered protoss there and gained the respect of the valiant Executor Tassadar. Raynor's bluff honesty enabled him to forge a bond between Tassadar and the dark templar Zeratul.
Raynor and his troops went on to fight alongside the protoss in several campaigns and played a key role in battling the United Earth Directorate incursion that followed. A twist of fate found Raynor temporarily allied with Arcturus Mengsk and the Queen of Blades, the being reforged from Sarah Kerrigan by the zerg Overmind. Although these two tyrants fought against a common foe, it was only a matter of time until their tenuous alliance collapsed. In the end Kerrigan was the one who turned against her erstwhile allies and struck the first blow, and many of Jim Raynor's comrades died to her treachery.
Raynor escaped the massacre and vowed to have vengeance at some day in the future. Even so, against the full strength of the zerg Swarm and the vast psionic powers of the Queen of Blades, his chances seemed slender at best. Eventually, exhausted and disillusioned, Raynor returned to terran space to lead a resistance movement against the spreading power of Arcturus Mengsk's Terran Dominion. Over the years this fight hasn't gone well. Arcturus Mengsk has used his greatest weapons – oratory, the media, and propaganda – to marginalize Raynor's efforts.
Raynor's Raiders remain public enemy number one to the powerful Terran Dominion. Mengsk sees Raynor's continuing existence as a challenge to his authority. However, Mengsk is also wary of creating a martyr by having Raynor assassinated, and so he has taken steps to keep Raynor and his followers constantly hunted and harried and deny them any chance to gain a respite and build their strength.
Years of skirmishing with the inexhaustible resources of the Dominion has whittled down Raynor's forces to a shadow of their former selves. Raynor has had to resort to occasional mercenary work just to garner enough funds to repair and rearm in the short term. Keeping his outfit running means that additional mercenary jobs will likely be needed in the future. Freedom isn't free.
Today Raynor seems to be losing faith: he's drinking heavily and blames himself for Kerrigan's being taken by the zerg. His hatred for Arcturus Mengsk has become a festering wound. Raynor's first officer, Matt Horner, still believes in him and in the revolution even though some of Raynor's doubts are spreading to his crew. Horner has done a lot to keep things going over the years, always having faith that Raynor's innate heroism will resurface and lead the rebels to victory.
Raynor is a good leader and an excellent tactician although he lacks any formal training or background. He has learned his skills through experience, and so he is unfettered by preconceived notions of what "the book" says is the right or wrong approach. Raynor will seldom plan things out in very much depth, but he has an excellent ability to improvise and turn the tables in a situation by using whatever he has at hand.
Raynor is also a man with a past. He is a known associate of notorious convict Tychus Findlay, the pair of them having served together in the 321st Colonial Rangers Battalion "Heaven's Devils" during the Confederacy/Kel-Morian Guild Wars almost twenty years ago. Their first meeting was in the brig at Camp McIntyre while serving 30 days apiece for insubordination.
Both men were listed as missing in action for almost nine months after a reconnaissance mission into Kel-Morian territory in the latter stages of the fighting on Mar Sara. Findlay was later turned over to the Confederacy by the Kel-Morians as part of a prisoner exchange after hostilities ceased. He was promptly incarcerated for desertion under fire. Exactly how Raynor managed to avoid Findlay's fate and land a job as marshal is unknown.
