Which Narnia novel is set mostly in Archenland and Calormen?

The Narnia novel set mostly in Archenland and Calormen is *The Horse and His Boy*.

Published in 1954, it follows Shasta, Aravis, and the talking horses Bree and Hwin as they flee Calormen and travel north. Much of the story unfolds in Calormene locations such as the capital, Tashbaan, before the characters cross the desert into Archenland.

The novel’s central conflict involves Prince Rabadash’s plan to invade Archenland and reach Narnia. Shasta’s warning helps King Lune prepare for the attack, while the story eventually connects with the Pevensies in Narnia. That setting makes the book unusual among the Chronicles: it focuses on southern countries and mostly new characters rather than beginning with children from our world.

A common mix-up is calling it a book set mainly in Narnia. Narnia is important to its conclusion, but Calormen and Archenland dominate the journey and political plot.