A fundamental truth about Britain in the 19th century is that it was a global power and, according to many scholars, was alone amongst the nations of its day in holding that status. This pre-eminent position rested on Britain's ability to project military - primarily naval - force, on its financial and economic dominance, the resources of a worldwide empire, and diplomatic prestige. At a certain point these material levers of power began to wane, but exactly when - and to what extent - that change occurred is contested.
As the 20th century dawned, contemporary observers believed they were already at a turning point, as Britain's global dominance came under increasing challenge. Military setbacks during the Boer War raised questions about the nation's ability to defend itself, while the poor physical condition of many volunteers caused anxiety about their fitness to perform in the workplace, as well as their capacity as soldiers. These concerns in turn provoked the Condition of England and National Efficiency debates, the latter fuelled by growing awareness of the threat of economic competition from rising industrial nations like Germany, France, USA and Japan. Financial burdens imposed by the Great War saw the mantle of world's financier pass from Britain to the USA, while having to assume responsibility for some of Germany's former colonies exacerbated the pre-war problem of imperial overstretch. At the same time, former imperial ties began to loosen as the white Dominions and India sought greater autonomy. These strains were increased by the huge national effort expended in 'holding the line' during World War Two. Britain's post-war weakness, laid bare by the outcome of the Suez Crisis, was underlined by former US Secretary of State Dean Acheson's brutal assessment that 'Britain's attempt to play a separate power role...is about played out' (Speech to West Point Military Academy, December 1962).
But there is another narrative of Britain's global role in first half of the 20th century. This version points to the nation's ability to adapt to a world environment transformed by the upheaval of two world wars, to reinvigorate its economy and revive its international influence by mobilising the levers of 'soft power' - cultural assets, scientific-technical and educational expertise, diplomatic skills, and reputational credit (e.g. based on solid legal and political institutions, membership of key international organisations such as UN, NATO, etc.). We shall compare the arguments of 'declinist' and 'revisionist' schools at various points, and conclude by debating whether the 21st century aspiration for a new 'global Britain' is based on illusion or reality.