gun was replaced by the improved and lighter Vickers and Lewis machine guns, the Brodie helmet was supplied for better personnel protection against shrapnel and the Mark I tank was invented to try to end the stalemate of trench warfare. The vast majority of the British Army fought in France and Belgium on the Western Front but some units were engaged in the Mediterranean, the Middle East, Africa and Mesopotamia, mainly against the Ottoman Empire. One battalion also fought in China during the Siege of Tsingtao. Inter-war period (1919–1939) Organisation In 1919–1920 there was a short-lived boom in the British economy, caused by a rush of investment pent-up during the war years and another rush of orders for new shipping to replace the millions of tons lost. But, following the boom, interwar Britain faced serious economic woes beginning with the Depression of 1920–1921. Heavy defence cuts were consequently imposed by the British Government in the early 1920s as part of a reduction in public expenditure known as the "Geddes Axe" after Sir Eric Geddes. The Government introduced the Ten Year Rule, stating its belief that Britain would not be involved in another major war for 10 years from the date of review. This ten-year rule was continually extended until it was abandoned in 1932. The Royal Tank Corps (which later became the Royal Tank Regiment) was the only corps formed in World War I that survived the cuts. Corps such as the Machine Gun Corps were disbanded, their functions being taken by specialists within infantry units. One new corps was the Royal Signals, formed in 1920 from within the Royal Engineers to take over the role of providing communications. Within the cavalry, sixteen regiments were amalgamated into eight, producing the "Fraction Cavalry"; units with unwieldy titles combining two regimental numbers. There was a substantial reduction in the number of infantry battalions and the size of the Territorial Force, which was renamed the Territorial Army. On 31 July 1922, the Army also lost six Irish regiments (5 infantry and 1 cavalry) on the creation of the Irish Free State. Until the early 1930s, the Army was effectively reduced to the role of imperial policeman, concentrated on responding to the small imperial conflicts that rose up across the Empire. It was unfortunate that certain of the officers who rose to high rank and positions of influence within the army during the 1930s