Sharpe's Siege (#9) - Bernard Cornwell

Sharpe's mission has seemed simple: capture a small unguarded French coastal fort, cripple Napoleon's supply lines, and retreat across the sea. But behind the lines, Sharpe's old enemy, Pierre Ducos, awaits Sharpe's arrival with a battalion of French soldiers and a vicious commanding general who keeps the scalps of his dead enemies as trophies.

Outmaneuvered by Ducos's treachery and abandoned by his own navy, Sharpe has only two choices: to escape with the aid of the charming, unscrupulous American mercenary, Cornelius Killick, or die.