The Fortune of War (Aubrey-Maturin series, Book 6)

This time it's the War of 1812 that gets in the way of Captain Jack Aubery's plans. Caught en route to England in a dispatch vessel, Aubrey and Maturin are soon in the thick of a typically bloody naval engagement. Next stop: an American prison, from which only Maturin's cunning allows them to engineer an exit.