Malaria Influenced Outcomes of Yorktown Sieges: 1781 and 1862

During two critically important battles on the Yorktown peninsula in Virginia in 1781, during the American Revolutionary War and in 1862 during the US Civil War, malaria played a vital role in determining how many soldiers were fit to fight. Lord Cornwallis' British Army was besieged by a Franco-American Army under Washington and forced to surrender when the Royal Navy could not relieve them. At the time of the October capitulation, most British soldiers were sick from fevers probably due to malaria whereas less than 8% of American soldiers were ill. This differential disease effect was likely due to lower exposure and partial immunity in the Americans. A very different military campaign in the same area was also disrupted by malaria more than 80 years later during the US Civil War. General McClellan failed in his attempt to capture the rebel capital at Richmond when forced to camp in the swamps of the Chickahominy River by Confederate defensive works leading to a malaria epidemic in summer 1862. Disease did not solely determine the military outcome, but malaria strongly influenced how many soldiers could be maintained in a field army. Malaria remains capable of causing mass casualties in deployed military forces.