Eyes of the Emperor by Graham Salibury. A Japanese-American boy in Hawaii, Eddy Okubo, experiences the Japanese bombing of Pearl Harbor, lies about his age, and joins the Army. Because of his ethnic background, Eddy is given a special assignment that tests his commitment, patriotism, and endurance.
Code Talker by Joseph Bruchac. A Navaho boy, Ned Begay, hears about the Japanese attack on Pearl Harbor, disguises his age, and joins the Marines. Because of his ethnic background and fluency in the Navaho language, Ned is given a special assignment that tests his commitment, patriotism, and endurance.
I read both of these in quick succession and found them to be similar in tone and in plot, but I liked both anyway. I would imagine that if you know any boys who are WWII buffs, these would be great to recommend.