As the British death toll, largely caused by yellow fever, continued to climb, Pitt was criticised in the House of Commons. Several MPs suggested it might be better to abandon the expedition, but Pitt insisted that Britain had given its word of honour that it would protect the French planters from their former slaves, and the expedition to St. Domingue could not be abandoned. The British attempt to conquer St. Domingue in 1793 ended in disaster; the British pulled out on 31 August 1798 after having spent 4 million pounds (roughly £ million in today's money) and having lost about 100,000 men − dead or crippled for life, mostly from disease – over the preceding five years. The British historian Sir John William Fortescue wrote that Pitt and his cabinet had tried to destroy French power "in these pestilent islands ... only to discover, when it was too late, that they practically destroyed the British army". Fortescue concluded that Pitt's attempt to add St. Domingue to the British empire had killed off most of the British army, cost the British treasury a fortune and weakened British influence in Europe, making British power "fettered, numbered and paralyzed", all for nothing.