Sharpe's Havoc by Bernard Cornwell

Sharpe's Havoc: Richard Sharpe and the Battle of Oporto is a historical novel by Bernard Cornwell set during the Napoleonic Wars. It is the twentieth full-length novel in the series (in order of publication), and takes place between the events of Sharpe's Rifles and Sharpe's Eagle. The book is set largely in Portugal during General Arthur Wellesley's Oporto Campaign in 1809.

History comes dangerously alive in this "New York Times" bestseller as Sharpe returns to the battlefields of the Iberian Peninsula, to battle against Napoleon's invasion.