Sharpe's Skirmish by Bernard Cornwell

Sharpe's Skirmish: Short Short (Richard Sharpe Adventure Series) - Sharpe is assigned to guard the recovery of muskets at a small decaying fortress in San Miguel.  He was given the light duty so that he may recover from his injuries suffered in Salamanca.  No one believes the French are near and they all believe they are safe.  Sharpe's intuition tells him otherwise and prepares to defend the fort.  Of course his intuition is right and the French attack in force and overtake the Sharpe's small company and the fort.  However, Sharpe doesn't give up easily and plans to take the fort back while waiting for reinforcements from Salamanca.