At the start of 1939, the British Army was, as it traditionally always had been, a small volunteer professional army. At the beginning of the Second World War on 1 September 1939, the British Army was small in comparison with those of its enemies, as it had been at the beginning of the First World War in 1914. It also quickly became evident that the initial structure and manpower of the British Army was woefully unprepared and ill-equipped for a war with multiple enemies on multiple fronts. During the early war years, mainly from 1940 to 1942, the British Army suffered defeat in almost every theatre of war in which it was deployed. But, from late 1942 onwards, starting with the Second Battle of El Alamein, the British Army's fortunes changed and it rarely suffered another defeat.
While there are a number of reasons for this shift, not least the entrance of both the Soviet Union and the United States in 1941, as well as the cracking of the Enigma code that same year, an important factor was the stronger British Army. This included better equipment, leadership, training, better military intelligence and mass conscription that allowed the army to expand to form larger armies and army groups, as well as create new specialist formations such as the Special Air Service (SAS), Special Boat Service (SBS), Commandos and the Parachute Regiment. During the course of the war, eight men would be promoted to the rank of Field Marshal, the army's highest rank.
By the end of the Second World War in September 1945, over 3.5 million men and women had served in the British Army, which had suffered around 720,000 casualties throughout the conflict.
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