The Walcheren Expedition of 1809 saw the British military land 40,000 troops on the marshy Dutch island of Walcheren in an attempt to open a second front against Napoleon and destroy his naval base at Antwerp. While military operations initially met little French resistance, the British command committed a catastrophic logistical blunder regarding fresh water supply. Walcheren was a low-lying island surrounded by salt water and dominated by stagnant, brackish marshes.
British planners assumed the invasion force could secure adequate potable water from local wells and surface streams. In reality, the local groundwater was severely contaminated and polluted by brackish seepage. As tens of thousands of soldiers encamped in the summer heat, well capacity collapsed, and soldiers resorted to drinking contaminated surface ditch water.
The resulting epidemic—a combination of malaria, typhus, dysentery, and paratyphoid known as Walcheren Fever—decimated the ranks. British supply ships carrying freshwater barrels were bogged down by bureaucratic delays and adverse naval winds in the North Sea. Out of more than 4,000 British fatalities during the campaign, only 106 soldiers died in combat; the remainder succumbed to disease directly exacerbated by the total collapse of freshwater distribution.
The disaster led to a parliamentary inquiry and permanently altered British military medical logistics.