What is the main conflict in Sharpe's Waterloo: Richard Sharpe and the Waterloo Campaign by Bernard Cornwell?

SHARPE'S WATERLOO by Bernard Cornwell is an account of the four days in June 1815 when the allied armies under the Duke of Wellington confronted the Emperor Napoleon as he and his troops marched on Brussels, the capital of Belgium. The story is told through the eyes of Richard Sharpe, a veteran British army officer who has been seconded to the staff of the young Prince of Orange.