Caspian was fair like most of the Telmarines. He was said to resemble his father.
In the movies, he had shoulder-length, wavy dark brown hair with brown eyes. In later movies, he had grown stubble and a short beard. Caspian was tall and muscular, though being slender and handsome.
Caspian was born the Crown Prince of the Narnian realm around 2290 NY. When Caspian was a small child, his father was murdered, and his mother died shortly after. Afterwards, he was raised as the nephew ("adopted son") and heir to his uncle Miraz, the "Lord Protector" of Narnia. As a prince, Caspian was raised under the care of his nurse, who spent many hours playing games with him and telling him tales of the Old Days of Narnia. These stories sparked a deep longing in Caspian for those Old Days, but he felt sure they would never come back.
Caspian spent very little time with his aunt, but twice a week his uncle would take him on a walk for half an hour, and talk to him. On one such day spent with his uncle, he revealed that he had been told stories about the land of Old Narnia and about the Kings and Queens who ruled it, and most importantly, about Aslan. Caspian believed what his nurse told him, telling his uncle that the stories were real history. Shortly afterwards, Miraz removed Caspian's Nurse as a punishment to both of them, and replaced her with a tutor.
Though Caspian was horrified to lose his nurse, he came to like his tutor, an old man called Doctor Cornelius. The doctor taught him many topics including grammar, astronomy, history, and politics (though of navigation he learned nothing, because the Telmarines hated the sea). As soon as his schooling began, he was also taught nonacademic but princely pursuits such as horseriding, archery, swordplay, and music. Despite his nurse's absence, Caspian did not forget the tales she told him, though he was careful not to speak of them, having learned that Miraz disapproved of such things. During one history lesson with Doctor Cornelius, Caspian asked his professor hopefully whether the old stories might be true and whether Cornelius would tell him more. The professor's reply was cryptic and unsatisfying.
A few nights later, Cornelius roused Caspian and took him to a secret tower for an astronomy lesson. While there, Cornelius led Caspian to guess that the old man was in fact a part-dwarf. His existence proved the truth of the old tales. From then on, Caspian and Cornelius would go often to the tower, and Cornelius would tell Caspian in secret much more about Old Narnia and its history. During this time, he begged Caspian in the future to be a better king than those before him, and to be fair to all. These meetings were of course kept an absolute secret from any others, and they strengthened the friendship between the prince and the professor.
The War of Deliverance
In 2303, when Caspian was around fifteen, his uncle Miraz's wife gave birth to a son. On the night of the birth, Caspian was roused by his professor and dressed in traveling clothes before being led to the tower again. There, Cornelius told him of the birth and for the first time confirmed the danger Caspian was in. Miraz had murdered Caspian's father for the throne. Now, with an heir of his own, Miraz would willfully murder Caspian so that his son would carry his line. Cornelius urged the prince to flee that very night, giving him advice, money, and the magic horn of Queen Susan. Caspian fled alone into the woods, where he was caught in the midst of a storm and hit by a tree, throwing him from his horse. When he woke, he was in an unfamiliar home being tended to by three strangers. His rescuers were Old Narnians, Trufflehunter the badger, Trumpkin the red dwarf, and Nikabrik the black dwarf. When he announced his own identity, they disagreed about what to do with him, but eventually agreed to take him as their own king if their fellow Old Narnians agreed to it. After meeting with many Old Narnians, a deal was struck. Caspian would be the Narnian's king and leader and give them their freedom if they would fight for him and give him back his kingdom. Everything was agreed, they would be loyal to Aslan.
After coming to an agreement, the Narnians were joined by Doctor Cornelius, who had fled for his own life. He warned them that Miraz knew of their doings and intended to attack and kill them all. The Narnians fled to the hallowed site of Aslan's How and prepared for battle. For several weeks the Narnians unsuccessfully battled the Telmarines before Caspian and his advisors decided to blow the magic horn of Queen Susan in the hope that they would be answered with a powerful form of high magic. Two scouts were sent out to discover the results of the experiment, and for several days they waited.
When no response came, Nikabrik proposed that they call on yet another power, the evil white witch. When Caspian and his fellows refused, Nikabrik and his companions (a hag and a were-wolf) attacked them. Caspian was attacked by the were-wolf, but rescued by the arrival of one of his scouts bringing back the Kings and Queens of Old, summoned by the blow of the horn. After saving Caspian's life, the High King Peter introduced himself and set plans to defeat Miraz in a champion's duel.
Later that day, the duel was held, and Caspian witnessed it alongside King Edmund and Doctor Cornelius. Eventually the duel was disrupted when Miraz was killed by one of his own men, and battle was joined. Caspian fought alongside the two kings for a few moments before the Telmarine Army retreated in the face of the attacking Narnians. Shortly afterward, Aslan and the Queens of Old (Susan and Lucy) cut off the Telmarines' escape route, and the army was captured.
On that day, the 12th of Greenroof, 2303, Caspian first met Aslan and was made a knight by the High King Peter. A few days later, the kings and Queens of old returned to their own world, and the most hostile Telmarines were sent out of the country. Caspian was shortly thereafter made King of Narnia. Therefore Narnia's sixth era had begun.