In May 1809 the Secretary of State for War, Lord Castlereagh, offered Chatham the command of an amphibious assault aimed at destroying the French fleet and fortifications around Antwerp and the island of Walcheren. Chatham commanded the largest expeditionary force Britain had yet fielded in the war. Despite early success in taking the town of Flushing, the campaign was an unmitigated disaster. The army made slow headway and the French immediately withdrew their fleet to Antwerp, a tactic that should have been foreseen by the politicians, admirals and generals planning the campaign from the start. While Chatham quarrelled with the naval commander, Sir Richard Strachan, as many as 8,000 British troops succumbed to malaria and other diseases.