What is the main conflict in Lieutenant Hornblower by C. S. Forester?

H.M.S. Renown sails from England in 1801 bound for Haiti. Her orders are to destroy privateers in the harbor of Santo Domingo and foment indigent rebellion against the Spanish colonizers. The voyage is interrupted by the captain's developing paranoia and an accident which incapacitates him. The lieutenants, led by Hornblower, take control of the ship and carry out the mission with uneven successes. Upon arrival in Kingston, Renown is received with honors and Hornblower is appointed as acting commander of a sloop-of-war. Temporary peace between England and France thrusts Hornblower and his particular friend Bush ashore on half-pay. Hornblower plays whist and gambles until hostilities resume.