When thinking of an eastern front, both political and military leaders had always to consider the position of the Soviet Union. During the 1920s and 1930s it would have been difficult to overlook the potential offered by the Soviet Union in any European combination, if only because of the implications of the Rapallo agreement. By the time of the Czechoslovak crisis it had been necessary to consider the possibility of the Soviet Union acting in defence of Czechoslovakia. The previous spectre of Russo-German collaboration had been on the whole dispelled by that time. Had the Soviet Union not been brought into the scope of France's European policies, her sheer geographical position east of Germany should have compelled most politicians to face the dilemma of the desirability or otherwise of courting Soviet assistance. And yet, on reflection, the remarkable feature of the period between May and September 1939 was that British politicians persuaded themselves of the non-existence of the dilemma posed by the absence of any commitment by Russia to European politics.

This unwillingness to envisage the possible consequences of excluding the Soviet Union from the scope of Britain's East European policy was never held with either equanimity or ease. Indeed, the question of the Soviet Union bedevilled all, if not most, Cabinet and Foreign Policy Committee deliberations during that time.