Walcheren Campaign 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 . Around 40 , 000 soldiers , 15 , 000 horses together with field artillery and two siege train s 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 . The Walcheren Campaign involved little fighting , but heavy losses from the sickness popularly dubbed " Walcheren Fever " . Over 4 , 000 British troops died ( only 106 in combat ) and the rest withdrew on 9 December 1809 . The primary aim of the campaign was to destroy the French fleet thought to be in Flushing whilst providing a diversion for the hard - pressed Austrians . However , the Battle of Wagram had already occurred before the start of the campaign and the Austrians had effectively already lost the war . The army was commanded by John Pitt , 2nd Earl of Chatham whilst the navy was commanded by Sir Richard Strachan . As a first move , the British seized the swampy island of Walcheren at the mouth of river Scheldt as well as South Beveland island , both in the present - day Netherlands . The British troops soon began to suffer from malaria ; within a month of seizing the island , they had over 8 , 000 fever cases . The medical provisions for the expedition proved inadequate despite reports that an occupying French force had lost 80 % of its numbers a few years earlier , also due to disease . The French forces were commanded by Jean - Baptiste Bernadotte , who had just been stripped of his command after disobeying orders at Wagram . Dismissed from Napoleon ' s Grande Armée , Bernadotte returned to Paris and was sent to the defence of the Netherlands by the council of ministers . He led the French forces competently and although the British captured Flushing , after a ferocious bombardment , and surrounding towns on 15 August , he had already ordered the French fleet to Antwerp and heavily reinforced the city . With the main objective for the British out of reach , the expedition was called off in early September . Around 12 , 000 troops stayed on Walcheren , but by October only 5 , 500 remained fit for duty . In all , the British government spent almost £8 million on the campaign . Along with the 4 , 000 men that had died during the campaign , almost 12 , 000 were still ill by February 1810 and many others remained permanently weakened . Those sent to the Peninsular War to join Wellington ' s army caused a permanent doubling of the sick lists there . Naval forces . In addition to the large number of naval vessels , customs - house and excise cutters participated , as did a packet ship . The City of London , Loyal Greenwich , and Royal Harbour River Fencibles also contributed men to the expedition . Irish legion . The 1st battalion of the Irish legion ( raised for an invasion of Ireland that never happened ) was stationed in Flushing during the assault , and was therefor almost completely captured . However , two officers went into hiding with the regimental eagle , and after a few days they crossed the river and escaped towards the south . Napoleon gave them the Légion d ' honneur and a promotion as a sign of gratitude .