amphibious warfare asiento austria battle of bloody marsh blas de lezo caribbean caribbean basin cartagena colombia dysentery edward vernon george ii of great britain havana italy kingdom of great britain maria theresa oceanic basin plantation prime minister of the united kingdom prussia richard lestock robert walpole silesia spain spanish armada spanish main spanish west indies starvation tobias smollett united states marine corps viceroyalty of new granada virginia war of the austrian succession yellow fever