I forgotted much of the novel but the general story is that the MC gets transmigrated as a prince who is exiled from the Kingdom along with his mother who was a maid and with some other people. The MC is given a worthless land and he also has a system for Kingdom development. The MC uses the system to bring modern technology and weapons in his Kingdom and later on the king wants the land back and launches a attack but ii defeated. Some other things in the novel are: The king had actually killed his brother to get the throne and the true heir to the throne of a good friend of MC and also a rebel The mother end of marrying the general who came with the prince during his exile. Kings and Queens of other nation come to the MC's Kingdom to work as a commoner
Theres one that reminds me of this. The way it went is that the prince had a shit power, like alchemy or something; he was exiled to be the lord of some rural town, and when they arrived the town was being attacked by bandits and the first thing they do is like, build a war or something? Does that ring a bell with the one you're thinking of at all?
I am the king of technology dude brings the 21st century in that wold and its not that the other kings and queens comes to work as commoner but our MC saves them and make them take refuge until they get their country back apparently its our mc task to save the chosen ones, so that he can bring their country on a right track and our MC is making UNO