Monk by William O'Connor
Although the Tome of Battle is pretty much setting-free, its ideas do incorporate a sense of history in its pages: the disciplines of the Sublime Way count hobgoblin practitioners as their earliest devotees, and the legacy weapons and prestige classes give a sense of shared stories among ancient warrior societies.
I think that immersing the disciplines and prestige classes into the world can help give a sense of backstory encouragement for gaming groups. Although many archetypes can serve as generic replacements for standard warriors, dedicating martial schools, societies, and the like to the realms enmeshes it in the world much as the gods and fantasy races.
Martial Adepts in the Realms
The art of war is something virtually every culture of Faerûn knows well, and the myriad styles of battle are nearly uncountable. From the slave-gladiators of Thay who delight at the roar of the crowds to the gnomish gunsmiths of Lantan, warriors defy easy categorization.
Still, like the Art of magic, there was a common thread linking this universal desire of power and conflict, which came to be expressed in the human Reshar's writings of the Sublime Way. The Temple of Nine Swords in the Galena Mountains of Damara united warrior-scholars of these traditions together before its untimely demise. Although their foundations crumbled and treasured swords were scattered to the four winds, the disciples carried their teachings on the open road and penned their secrets in scrolls for others to learn. Nowadays one can find warpriests and crusaders trading spells and maneuvers in Tempus' sacred halls, and the hardened hobgoblin warlord is just as likely to know the ways of Iron Heart as an Illuskan sellsword. Just like the desire for conflict, the art of the Sublime Way transcends cultural boundaries with only dedication and willpower remaining the primary obstacles for those willing to learn.
Crusaders: Although not always bound to the tenets of Law and Good, the crusaders' zeal burns just as passionately as any paladin's. Their number can be found among warriors who court the favor of the gods, and those deities who value straightforward might count the most crusaders. Those of Tempus exult in the battle itself, fighting for all manner of causes and each other so that they may achieve glory and enlightenment.
A few belonging to Tyr's service are surprisingly adept with one-handed weapons in emulation of their patron. The Order of the Single Blade takes an unorthodox approach to enforcing Tyr's will, adopting the ways of the duelist and relying upon their holy endurance to protect them all the way.
The Iron Fasces are an international organization of Zhentarim soldiers dedicated to Bane. Emphasizing the group tactics of the White Raven, they seem to act as one with near-supernatural clarity. Combined with the wealth and political clout of their superiors, they are some of the most feared warriors in the Dalelands and Moonsea regions.
Swordsage: Blending the mundane and supernatural with their practices, swordsages are the most cerebral and least-understood of martial disciples. It is quite common for folk to mistake them for monks, and while it is true that some of them pursue physical and mental perfection to achieve enlightenment it is by no means the only path.
The Scholars of Illmater are humble folk who seek out society's disenfranchised elements. From the slums of great cities to refugee colonies in need of aid, they protect these communities from all manner of evil, be it organized crime elements to predatory monsters thinking that their targets won't be missed. Using nothing but their bodies and conviction, these swordsages give hope to the powerless, that one does not wealth or magical might to fight for one's beloved.
Somewhere within the Underdark is a conspiracy of drow outcasts fallen out of Lolth's favor. Unable to join her priesthood nor learn at the arcane academies, they sought out other means of power and found the old scrolls of a Shar cult. In a realm of eternal night the Shadow Hand discipline is might, and the masked agents are sowing discord among the many cities of the Spider Queen.
Warblade: A warblade is not identified as such by their fighting expertise, nor by the disciplines they know. A master swordsman may gain many titles, but how he fights determines whether or not he wears this title. When you see a knight in shining armor, you see a warrior. When you see a knight who fights with passion, whose form in the chaos of bloodshed and death is darkly beautiful in its execution, you know you're viewing a warblade in action.
Aided by the oversight of ancient and magically-adept dragons, the Blood of Morueme counts many hobgoblin warblades among its number. True to tradition they are all skilled in the Iron Heart discipline. Many an orcish chieftian or warmage has looked on in horror when otherwise-insignificant goblinoid grunts shrugged off grievous blows and spells with nothing more than sheer will.
Thanks to their long lifespan and emphasis on swordplay and dancing, the worshipers of Eilistraee find the Diamond Mind discipline a natural fit. Emphasis on grace and perception in battle complements their traditional fighting arts, and folk of Waterdeep often tell tales of dark elves who strangely come to the aid of lone wanderers beset by monsters. Armed with nothing but swords they manage to slay dire animals and aberrations to the shock of onlookers.
The Disciplines in the Realms
Desert Wind: The genasi who claim lineage to the mighty efreet ply the forlorn roads between Calimshan's bastions of civilization. They seem unaffected by the elements, even less so than most planetouched, and many a foolish brigand or greedy sultan sought to extract wealth and tribute from them. Every act was met with failure, for these genasi commanded the very element of fire itself.
Practitioners of the Desert Wind now live far beyond their homeland, men and women of humble means with a reverence for nature and its power. They are willing to teach those who share common ground, as well as some wayward sorcerers and genasi of similar heritage in need of controlling their inborn powers.
Devoted Spirit: From as far back as old Netheril to as recent as the Time of Troubles, it became apparent that the power of deities, however mighty they may be, can call just as much as anything else in the world. The practice of drawing divine magic from one's patron deity via inner wisdom is a potent tool, but it is not the only way of forging a connection with the gods. A few pious mortals throughout Toril's history found favor shining upon them, even if they lacked the gifts of divine magic. By drawing on one's own inner spirit and dedication to the moral tenets of the multiverse, martial adepts could channel holy and unholy energy into themselves.
Diamond Mind: Practitioners of this discipline act as quickly as they think, their counters and strikes to fast and precise only other skilled warriors have a chance at noticing their blows, much less deflecting them. Many elves who take up the blade gravitate to this school, and some of the earliest historical records of its techniques can be found in the halls of Myth Drannor. Diamond Mind is also popular among the noble courts of countless nations and the Strongheart halflings of Luiren.
Iron Heart: Historically forced into extreme living conditions, the hobgoblins of Faerûn lacked the technological and magical edge of their human, dwarven, and elven enemies. Instead they adopted a martial culture to ensure that all among their number would be ready and willing to die for their clan. A particularly fearsome and prosperous tribe in the Nether Mountains of the North erected a monastery which gave birth to what we now know as the Iron Heart discipline. Other civilizations which fought against the goblins sought to learn their language and culture so as to better defend against them. The human scholar Reshar learned of Iron Heart and taught it to the other races in his Temple of the Nine, a fact which fills many hobgoblins with anger at their ways being stolen.
Setting Sun: In a world full of humanoids at least twice their size, the halflings knew early on that they could not rely on strength alone to survive. While witnessing the martial techniques of monks in a monastery, a strongheart halfling by the name of Forrick Greenberry came upon a realization. The use of deception against a much stronger and larger opponent in melee could give rise to potentially devastating consequences as their own size and strength were turned against them. He took his findings to the clerics of Yondalla, who taught it to the farmers and laborers of their communities and the rest is history.
In spite of its halfling origins, other small races have adopted Setting Sun techniques as well, and its emphasis on unarmed trips and maneuvers makes it a favored school for peasants and other folk whose background denies them easy access to quality arms and armor.
Shadow Hand: It is hard to research this discipline's history with any degree of accuracy, for several groups lay claim to its invention. Shar claims that it is a manifestation of her will; a few genealogical records of Tethyrian noble families point to its more martially-inclined members becoming one with the darkness to bring woe upon rival houses; finally, the Shadow Thieves of Amn count more than a few members who bring the chilling touch of night with their poisoned blades.
In spite of its sinister reputation, the Shadow Hand discipline is not intrinsically evil, and some more moral swordsages value its uses when one must walk in darkness.
Stone Dragon: Focusing on sheer power and a physical connection with the land itself, the dwarves of the ancient empire of Bhaerynden mastered the precursor of this discipline. From the shield dwarves of the North to the gold dwarves of the Great Rift, all clans share a common legend of the Wardens of the Mountain. By drawing upon the surrounding stone which comprised reality as they knew it, the Wardens gained an almost druid-like union with the rock and accomplished mighty deeds impossible for their strength and size.
Today the Stone Dragon discipline can be found among tutors in every significant dwarven hold, and more than a few Underdark races learned of it themselves by trading and stealing dwarven secrets.
Tiger Claw: The many tribes of Uthgardt barbarians long respected the power and cunning of nature's predators, and the Red Tigers sought to emulate their totem animal. Focusing on vicious speed, vaunting leaps, and twin strikes, the Red Tigers more than lived up to their name with their favored discipline. Sometimes a member of this tribe might teach what they know to a fellow Uthgardt or the rare warrior who has earned their respect. Worshipers of Malar and various lycanthrope tribes also adopted this discipline, turning its power to their own deadly use.
White Raven: It was said that long ago a valiant general finally gave way to despair. Even though she knew her cause was just and that her side's loss would lead to great suffering, the horrors of war seemed unending, that every victory of today would be washed away by the tragedies of tomorrow. She prayed to Lathander for guidance, and was answered by the omen of a white raven.
"Do not despair," the raven said, "for your trials today bring peace and prosperity to the people of the future. Without the shining light of Good, the world would be a bleak field of unending sorrow."
At this point she realized that her despair blinded her to her own accomplishments. Tomorrow she marched into battle, filled with new purpose, and her hope gave strength to the soldiers who marched before her. The story of the White Raven is is a noble tale of how one person's efforts can aid another, turning the tide of battle. The leaders of Evil change the tale to suit their own agendas, but military historians who study the lore of this era gain insight into battle.
What the Future has in store for us
I hope you enjoyed this read. If I feel the inspiration I might write similar articles for other official and non-official settings. Generally speaking I plan on matching Tome of Battle with pre-Pathfinder 3rd Edition worlds, Path of War with Pathfinder worlds. But I may mix and match depending on what seems right at the moment.