The Walcheren Expedition of 1809 was arguably the single worst disaster to befall Britain during the entire French Revolutionary and Napoleonic wars. Conceived by Britain's Foreign Secretary Lord Castlereagh as a way of supporting Britain's embattled European allies against Napoleon, the expedition saw an army of 40,000 land on the inhospitable and marshy Dutch terrain around Flushing. There was fighting with the French, but the worst casualties were inflicted by disease. Dysentery and other infectious illnesses arising from the unhealthy swampland killed thousands and incapacitated many more, causing the abandonment of the inglorious expedition in circumstances resembling Gallipoli or Dunkirk more than a century later. This is an invaluable eyewitness account of the disaster.