In the summer of 1809, Great Britain dispatched over 39,000 soldiers to the swampy island of Walcheren in the Netherlands, aiming to open a second front against Napoleon and destroy the French fleet at Antwerp. However, the expedition quickly degenerated into one of the most disastrous military campaigns in British history due to malaria, typhus, and dysentery, collectively known as Walcheren Fever. What made the medical crisis dramatically worse was a bizarre and catastrophic breakdown in basic medical logistics, specifically regarding the supply of barley water and lemon juice.
Army surgeons relied heavily on barley water—a traditional soothing decoction used to hydrate feverish patients and mask the foul taste of tainted local water. Unfortunately, the medical board failed to ship adequate supplies of pearl barley, clean boiling cauldrons, or lemons across the North Sea. As thousands of soldiers collapsed daily, field hospitals ran entirely out of fresh water and basic dietary treatments.
Left with nothing but stagnant, brackish marsh water, sick soldiers were forced to drink contaminated fluids, rapidly compounding dysentery and accelerating death rates. By the time the British army evacuated, over 4,000 men had died, with tens of thousands permanently debilitated, while fewer than 110 had fallen in actual combat against French forces.