After he leaves his own planet, the little prince first lands up on the planet of the king. The king can be compared to the prince himself. After all, they’re both royalty. But only the king makes a big deal of it. His “royal purple and ermine” robe (10.2) “crammed and obstructed” (10.8) his entire planet, leaving barely any place for the prince to sit down. As soon as he lays eyes on the prince, the king is thrilled to spot a subject. Then:
The little prince asked himself:
“How could he recognize me when he had never seen me before?”
He did not know how the world is simplified for kings. To them, all men are subjects. (10.4-6)
As the narrator explains, this king—like all other “kings”—thinks “all men are subjects.” The end. It’s really easy for any king to meet someone new and instantly place that person in a category: “Hooray! Here’s another subject!”
Indeed, this king sees subjects everywhere. However, his authority has a twist:
“For what the king fundamentally insisted upon was that his authority should be respected. He tolerated no disobedience. He was an absolute monarch. But, because he was a very good man, he made his orders reasonable.” (10.15)
By trying to be “reasonable,” the king ends up having no real power. He only gives orders that will be followed anyway. For instance, when the prince asks him to order a sunset, the king says he will order the sun to set when “conditions are favorable” (10.34)—that is, he will order the sun to set at the time when it will set in any case.
The king also doesn’t actually have any subjects. He’s the only person on his planet. Without the prince there, his only other potential subject is a rat. So, while the king claims to have power and absolute authority, he’s really all alone with nothing to rule over.
From an allegorical standpoint, the king symbolizes rulers who make a big deal about the power they have, but who in actuality are pretty ineffective at enforcing their power. It also mocks their grandiosity and showiness, which is kind of funny because they think they are way more important than they actually are. The king is somebody who thinks he’s boss, but he really isn’t.
It’s important to think of the king in relation to the time period in which this book was written. Saint-Exupéry wrote this book when he was an exile in the United States after the fall of France in World War II. Dictators like Hitler and Mussolini were gaining in power, and it appeared as if the Allies were powerless against their more brutal methods. The king, too, like France and Britain and the other Allies, is a reasonable and good man, but is hilariously ineffective.