In Days of Infamy, the logic of how the battle could have developed in Oahu is that the point of divergence occurs at a conference in March 1941, when Commander Minoru Genda and Admiral Yamamoto manage to convince the Imperial Japanese Army to follow up the Pearl Harbor air attack with an invasion to capture Hawaii whereas in reality, they did not.

As is usual in Turtledove novels, the action occurs from several points of view, including historical figures such as Minoru Genda and Mitsuo Fuchida.

In the meantime, the Imperial Japanese Navy destroys U.S. Admiral William F. Halsey's fleet by sinking the American carriers USS Enterprise and Lexington while they fruitlessly try to counterattack.

After weeks of fierce fighting and nowhere to retreat, U.S. forces on Oahu (led by Admiral Kimmel and General Short) surrender and the Territory of Hawaii is annexed to Japan.

With the United States' main forward base in the Pacific conquered and much of its fleet crippled beyond repair, this allows Japan to dominate much of the southern Pacific Ocean almost unopposed from successfully defeating the British in the Indian Ocean, occupying all of New Guinea and the Dutch East Indies, attacking Australia, capturing Wake and Midway Islands, and having the ability to launch bombing raids on the West Coast of the United States.

The novel ends when, as was common in their other occupied territories, the Japanese create a puppet government which is the revived Kingdom of Hawaii, ruling through a member of the Hawaiian Royal Family installed as King in the Iolani Palace; The Americans back on the mainland, humiliated by their losses to the Japanese, swear revenge and begin a massive military buildup that sets the stage for the second novel.

By mid-1943, Japanese occupation of Hawaii has brought a toll of strict food rationing, severe martial law, and American prisoners (military and civilian) suffer abuses from their occupiers.

Most important, Japanese officials and their Hawaiian collaborators escape on a submarine as Honolulu falls, but Minoru Genda and the King and Queen of Hawaii choose to commit suicide.

By the end of the novel, it appears that there will be no major Nisei combat forces, and that most ethnic Japanese will be shipped from Hawaii to join those in relocation centers in the United States, a blow to civil rights in postwar America.

Joe Crosetti (vp) — Son of a San Francisco fisherman who enlists after Pearl Harbor and eventually flies a Grumman F6F Hellcat fighter.

Kenzo Takahashi (vp) — Born in Hawaii and, thus, a U.S. citizen, Ken sees Japan as enemy nation, especially after his mother is killed by a Japanese air raid on Honolulu.