Historian Keith Nelson details the circumstances and traces the steps that led to the first significant accommodation and easing of tension between the superpowers during the Cold War. He shows that this occurred because historical developments combined in both countries to create a scarcity of the resources needed to maintain the existing activities of their societies, economies, and governments. Given ample means and apparent success, each nation would have almost certainly been inclined to continue established policies, even if these had meant perpetuation of the Cold War. But in the face of substantial shortages - deriving from setbacks with regard to domestic unity and morale, the performance of the economy, and relations with allies - realistically conservative leaders on both sides (those with little interest in transcendent change) found themselves irresistibly attracted by the possibility of an arrangement with their foreign opponent that would reduce the demands being put on them.