The Anglo-American alliance was dominated in 1943 by negotiations over the military strategy to pursue in the European theatre and by the basis for the reinstatement of British access to the secrets of the development of the atomic bomb from which they had been previously excluded. Against the backdrop of growing American power and preponderance in the alliance, Prime Minister Winston Churchill and President Franklin Roosevelt, along with their respective colleagues and subordinates, held a blizzard of meetings, conferences, and trans-Atlantic telephone calls supplemented by a stream of cables and dispatch of various emissaries to Washington and London. Churchill and the British argued in favor of the Mediterranean strategy and reliance on the strategic bombing of Germany, while the Americans supported a cross-channel invasion of the continent in 1944.
Philip Padgett links British support for the Overlord landings with the return to shared development of the Atomic Bomb in his book Advocating Overlord: The D-Day Strategy and the Atomic Bomb. It is an insightful study of the Anglo-American relationship from the Casablanca Conference until the last weeks of 1943. While the cross-channel invasion and atomic research were being negotiated simultaneously, Padgett lacks documentary evidence to completely make his case that Churchill sought a quid pro quo: British support for Overlord in return for renewed participation in the development of the atomic bomb. Padgett additionally provides interesting details about the constraints on Allied shipping as American divisions, soldiers and equipment, were transported to Britain in advance of the invasion of Normandy. Advocating Overlord is a fascinating narrative.