The seemingly boundless optimism and eschatological expectation that characterised the Edinburgh World Missionary Conference of June 1910 met its stark nemesis a little more than four years later. In August 1914, the German invasion of Belgium initiated a worldwide conflict that cost many millions of lives, profoundly changed the existing world order, and cast a long traumatic shadow on the twentieth century. The conflicts of the period from 1914 to 1945, which have been called ‘the second Thirty Years War’, echoed around the world, impacting most of the places where evangelicals had scattered their missions, churches, and communities over the previous 150 years. The first Thirty Years War in the seventeenth century saw ‘Christendom’ broken up and absorbed into single states of religious profession; this second one saw the emergence of the technocratic, secular state and the deterritorialisation of religion in the West. It also saw the ascendancy of nationalism as a quasi-religion, leading to the virtual deification of the nation-state – a trend that reached its most extreme manifestations in Nazi Germany and Fascist Italy, but was also very much apparent in the English-speaking world. The result for evangelicals was a set of catalytic experiences leading to crises of conscience, disruption to communities and adaptation to new circumstances.

At the same time, evangelicals faced the less brutal but eventually equally pervasive challenges of ideological and cultural change. The ramifications of Charles Darwin's theories on human origins and Karl Marx's on human society continued to reshape the intellectual and political worlds, even as the dissemination of the ideas of more recent thinkers such as Friedrich Nietzsche (1844–1900), Sigmund Freud (1856–1939) and Émile Durkheim (1858–1917) presented further radical alternatives to traditional frameworks of belief and understanding. The advance of technology not only transformed warfare with devastating results, but also profoundly changed peacetime life in developed societies. The advent of motorized road transport, the aeroplane, radio, cinema and eventually television transformed long-distance travel and communication and made the world much more interconnected. For evangelicals, the central dilemma was when to translate the literal warfare that dominated the age into a metaphorical warfare against mere innovation, and when effectively to engage modernity and turn it to their own ends.