Days of Infamy Series by Harry Turtledove

From Book 1: On December 7, 1941, the Japanese launched an attack against United States naval forces stationed in Pearl Harbor, Hawaii. But what if the Japanese followed up their air assault with an invasion and occupation of Hawaii? With American military forces subjugated and civilians living in fear of their conquerors, there is no one to stop the Japanese from using the islands' resources to launch an offensive against America's western coast.

Six weeks ago, Imperial Japanese military forces conquered and occupied the Hawaiian Islands. A puppet king sits on Hawaii’s throne, his strings controlled by the general of the invasion force. American POWs, malnourished and weak, are enslaved as hard laborers until death takes them. Civilians fare little better, struggling to survive on dwindling resources. And families of Japanese origin find their loyalties divided... moreSix weeks ago, Imperial Japanese military forces conquered and occupied the Hawaiian Islands. A puppet king sits on Hawaii’s throne, his strings controlled by the general of the invasion force. American POWs, malnourished and weak, are enslaved as hard laborers until death takes them. Civilians fare little better, struggling to survive on dwindling resources. And families of Japanese origin find their loyalties divided.Meanwhile, across the United States, from Pensacola, Florida, to San Diego, California, the military is marshaling its forces. Steel factories and fuel refineries are operating around the clock. New recruits are enlisting, undergoing rigorous training exercises. All for the opportunity to strike back and drive the enemy from American soil… less