The Irish Legion was a light infantry regiment in service of the French Imperial Army established in 1803 for an anticipated invasion of Ireland. It was later expanded to a four battalions and a depot, the legion won distinction in the Walcheren Expedition, the Peninsular War, and the German Campaign of 1813. Following the disbandment of the foreign regiments in 1815, the regiment's personnel were distributed.

The Walcheren Campaign was an unsuccessful British expedition to the Netherlands in 1809 intended to open another front in the Austrian Empire's struggle with France during the War of the Fifth Coalition. Sir John Pitt, 2nd Earl of Chatham, was the commander of the expedition, with the missions of capturing Flushing and Antwerp in the Netherlands and enabling navigation of the Scheldt River. Some 39,000 soldiers and 15,000 horses, together with field artillery and two siege trains, crossed the North Sea and landed at Walcheren on 30 July. This was the largest British expedition of that year, larger than the army serving in the Peninsular War in Portugal. Nevertheless, it failed to achieve any of its goals. The Walcheren Campaign involved little fighting, but heavy losses from the sickness popularly dubbed "Walcheren Fever". Although more than 4,000 British troops died during the expedition, only 106 died in combat; the survivors withdrew on 9 December.