Telmar

Telmar was an unstable colony of the Calormene Empire, within the World of Narnia, west of the Western Wild region and possibly on the coast of the Western Sea. However, later after the decay of its population, it was absorbed by outsiders. It became a seemingly Kingdom land until it was finally abandoned altogether due to subsequent centuries of disorder and, ultimately, a famine.

History of Telmar
Telmar, to the far west of the Kingdom of Narnia, was colonised first by Calormene settlers in Narnian year 300. After only two years however, Aslan made most of the inhabitants into dumb beasts because of their atrocious behavior. The turned voiceless animals soon destroyed each other and Telmarine society collapsed. The few that wern't changed, began an anarchist existance.

In 460, 12 seafaring pirates from Earth's "South Sea" arrived in the possibly oceanid land of Telmar, forcibly mixing their families with the desendants of the remaining Calormene settlers to make an intelligent (but also rough, brutal, and warlike) race of integrated Telmarine people. This had ultimately resulted in Telmar becoming a kingdom.

These were the Telmarines who grew strong in number and eventually invaded Narnia in Narnian-year 1998, during the Telmarine Conquest, after they left Telmar for good due to a famine in their home land. (It was from this line of Telmarines that Caspian X was descended.) The Telmarine invasion was made possible, in part, by the fact that the Kingdom of Narnia was suffering through a dark age, and so brought a new age to Narnia.

Telmarines, whose own country only had dumb beasts, were scared of Narnia's magical talking beasts and attempted to rid the conquered nation of them. However, in year 2303, these exiled "Old Narnians" who had lived in hiding since the Telmarine regime began, initiated the Narnian Revolution and defeated the Telmarine-Narnians. Telmar became a colony of the Narnian Empire, with the Western Wild region between the nations remaining uninhabited, as they could pass threw from Archenland.

The End of the Telmarines
After the Narnian Revolution, Aslan and Caspian X held a conference informing the Telmarines that those who don't want to remain in Narnia can exit through the portal that Aslan made. The Telmarine-Narnians that left Narnia consequently migrated back to their original island home in the South Sea whence their ancestors had come centuries ago as the villainous pirates from our world of Earth, which was apparently 80%. The fate of these departed Telmarine-Narnians remains unknown. According to Aslan the original race of pirates had long died out, and therefore the exiled Telmarines were not so vulnerable, when they were sent back to Earth to a plentiful land that had not yet been discovered by the people of Earth. Thus Narnia had begun its sixth era. The remaining 20% of Telmarines, where elected to remain in Narnia however.

Trivia

 * In the movie Prince Caspian, the Telmarines are interpreted as Spaniards because of their pirate origins.