Are there any novels about wars with other countries?

The recommended novels were The Demon-slaying War and My America. "The Demon-slaying War" was about a country on the edge of a "cliff". There was a group of contracted soldiers on the border, who ruled the world for the demons. The country was in danger. There was a description of the war. "My America" was also a story about war, and the main character was an arms dealer. I hope you like this fairy's recommendation. Muah ~😗