Crimson Tide — Richard P. Henrick

On the nuclear submarine USS Alabama, one man has absolute power. And one man will do anything to stop him.
A political coup in a shattered but still dangerous nation places the United States at deadly risk. Far beneath the ocean's surface, the USS Alabama receives orders to launch a preemptive nuclear strike against the besieged enemy capital. For departing Captain Ramsey, it is a final chance to the glory that no one will deny him. For Executive Officer Hunter, it is a monstrous directive without confirmation that must be disobeyed at any cost, before a world goes up in flames.
A command that cannot be rescinded is about to plunge the USS Alabama into a savage, bloody and terrifying war...with itself.