In 1934, Hore-Belisha became minister of transport, and in 1937 he succeeded Duff Cooper as secretary of state for war. Instructed by Prime Minister Neville Chamberlain to introduce "drastic changes"—as war seemed increasingly likely—Hore-Belisha improved conditions and training for ordinary soldiers, raised soldiers' pay, jettisoned many inefficient colonels and generals, upgraded officer training, and enhanced the army's mechanized warfare capabilities and capability to resist air attack. In April 1939, he prevailed on a reluctant Chamberlain to introduce conscription and to prepare a British Expeditionary Force (BEF) to fight in France if necessary. Although Hore-Belisha demonstrated innovation, decision, and vision within the army and outside it, his tactless style alienated many who essentially shared his views.
When war began in September 1939, Hore-Belisha criticized the hesitant preparations and progress of the BEF under the leadership of General Lord John Gort, chief of the Imperial General Staff. Hore-Belisha accurately predicted that, unless weak spots on the front were reinforced, Germany would probably attack successfully in the Ardennes sector. Gort and his allies, who included French army commander in chief General Maurice Gamelin, complained to King George VI, and in January 1940 Chamberlain reluctantly decided to remove Hore-Belisha from office. Hore-Belisha preferred to resign.
For the duration of the war, Hore-Belisha was one of Prime Minister Winston L. S. Churchill's strongest backbench critics, unsuccessfully urging Churchill's resignation after the fall of Tobruk in June 1942. From May to August 1945, Hore-Belisha served briefly as minister of national insurance, but he lost his seat in that year's elections. In 1954, he accepted a peerage, and his incisive parliamentary speeches regained him some political influence. Hore-Belisha died suddenly on 16 February 1957 while leading a parliamentary delegation in Reims, France.
Bond, Brian. British Military Policy between the Two World Wars. New York: Oxford University Press, 1980.; Hore-Belisha, Leslie. The Private Papers of Leslie Hore-Belisha. Ed. R. J. Minney. Garden City, NY: Doubleday, 1961.