What is the main conflict in Ship of the Line by C.S. Forester?

Captain Horatio Hornblower has recently returned from a successful cruise in HMS Lydia. News of his impressive successes fires the popular imagination and circulates in the Admiralty. Hornblower is appointed captain of HMS Sutherland, 74, and assigned to join a blockading fleet under the command of Rear Admiral Leighton. Hornblower pursues his duties with typical rigor and, when given brief detached command, conducts an astounding five raids in two days. He then rejoins the fleet and encounters four French ships-of-the-line. As the main body of the fleet attempts to close, Sutherland engages the entire French squadron, causing extensive damage to all enemy ships before becoming dismasted and ultimately wrecked. Hornblower finally strikes his colors and is taken into French captivity.