What boxed war game would you recommend for someone who's new to wargaming?

My nephew wants to get to war gaming but he's 10 years old so obviously large amounts of money are not available to him. He will play Gaslands, Heroquest, Car Wars, and other such boxed war games with me that I have but he like that get some of his own. The thing is though, I would like to get him something that would be easy to understand and easy to play since he's not always going to just be around me that I can explain to him the more complicated rules of something.