by Samuel R. Delany
Typical early 1960s science fiction.
"The Empire of Toromon had finally declared war. The attacks on its planes had been nothing compared to the final insult—the kidnapping of the Crown Prince. The enemy must be dealt with, and when they were, Toromon would be able to get back on its economic feet."
Add to this a radiation barrier that leaves a people isolated and an enemy called the Lord of the Flames and you're set up for epic battles and other fun geeky stuff.
This is considered the first of a trilogy, but quite honestly it didn't impress me enough to continue. None of the characters stood out for me and apart from an interesting contrast between the rich and the poor, the plot was fairly generic. There's also a mock-Arthurian Fantasy element in the young prince being kidnapped to be trained among the forest guardians to be a good king so the elements of a good story are there, but I found my mind wandering as I read. Somehow it just didn't grip me.
Very much a thing of its time.