Royal armies of the great western empire travel in style. Their camps are mobile cities, pavilions and pastures and even impromptu gardens raised for a week or a night by the Great King's magi, meant to house hosts numbered in the tens and hundreds of thousands. The Great King's officers ride in splendor, their armor fairly dripping with gold and jewels, and the sovereign himself shines like a second sun from his personal chariot, but even the meanest foot soldier of the host has a jeweled scabbard for his sword. The fighting men are only a fraction of the full population of such an army on the march, as slaves and hired hands guide the baggage animals, fetch water and food for the soldiers' mess. The nobles ride with whole retinues of servants, advisors and concubines--both male and female--in their tow, while the Great King attends his wars with even his close family in spectacularly luxurious tents the size of a splendid palace.
Often, the sheer glory of the marching army is enough to cow the Great King's foes. When that fails the storm of his archers' missiles and the spears of his shining, armor-sheathed cavaliers makes short work of even the most tenacious foes. When they fail, their commanders are executed for their obvious cowardice, and their heads paraded to encourage their replacements towards better results. When the royal army is led by the Great King himself, such force is mustered about the royal person that resistance crumbles like sandcastles before the rising tide. At least, until today.
Today, the Great King's army met a host out of the barbarian east with a fraction of its numbers, the mercenary vanguard of one of the empire's own rebellious satraps. The barbarians' armor shed arrows like inconvenient raindrops; their pikes slew both splendid cavaliers and the thoroughbreds beneath them. The Great King fled the field, abandoning his gilded chariot to the enemy's plunder, and with him fled the army's spirit. The royal host broke and ran before the barbarians, leaving the numberless servants and treasures of their camp to the tender mercies of the conquerors.
Your character was among those left behind. She might've been some high lord's lady, a concubine, a servant girl, one of the Great King's mage-priests, or even a rare woman-warrior from some far-flung outpost of empire. Whoever she was, she was captured in the royal army's rout and has fallen into the hands of a foreigner, maybe an officer, maybe a private soldier. She might welcome the change of circumstances, as a chance to be free from the cruel, haughty lords of the empire, or she might revile her captor. Regardless, she's become so much plunder in his keeping, to do with as he will.
