The Sum of All Fears by Tom Clancy

But too many groups have invested too much blood. Shunned by their erstwhile Soviet sponsors, increasingly isolated by the realignment of the Mideast, these terrorists have one more desperate card to play, requiring a degree of ruthlessness never before seen. With one terrible act, the world is plunged into an instant nuclear crisis -- and the floundering President is plunged into the ultimate nightmare. Forces collide. Shots are exchanged. What had seemed to be an isolated and horrible incident appears to each side as the incendiary mischief of the other. With the world poised on the brink of nuclear war, Ryan and his FBI counterpart, Dan Murray, frantically seek a solution before the chiefs of state lose control of themselves -- and the world.