Banished to the Empire's farthest outpost, veteran warrior Paulinus Maximus defends The Wall of Britannia from the constant onslaught of belligerent barbarian tribes. Bravery, loyalty, experience, and success lead to Maximus' appointment as "General of the West" by the Roman emperor, the ambition of a lifetime.

But with the title comes a caveat: Maximus needs to muster and command a single legion to defend the perilous Rhine frontier. On the opposite side of the Rhine River, tribal nations are uniting; hundreds of thousands mass in preparation for the conquest of Gaul, and from there, a sweep down into Rome itself. Only a wide river and a wily general keep them in check.

With discipline, deception, persuasion, and surprise, Maximus holds the line against an increasingly desperate and innumerable foe. Friends, allies, and even enemies urge Maximus to proclaim himself emperor. He refuses, bound by an oath of duty, honor, and sacrifice to Rome, a city he has never seen. But then circumstance intervenes. Now, Maximus will accept the purple robe of emperor, if his scrappy legion can deliver this last crucial victory against insurmountable odds. The very fate of Rome hangs in the balance.

A runaway Jumbo jet has crashed into the Capitol Building in Washington, leaving the President dead along with most of the Cabinet and Congress. Dazed and confused, the man who only minutes before was confirmed as the new caretaker Vice-President is told that he is now President of the United States.

President John Patrick Ryan must navigate the complexities of running a government without a government. Where do you begin? Ryan knows that the eyes of the world are on him now—and many of them are unfriendly. In Beijing, Tehran, and even in Washington, there are those eager to take advantage.

Soon, they will make their moves; soon, they will present Jack Ryan with a crisis so immense that even he could not imagine it.