Nineteen forty-eight saw the beginning of the systematic suppression of the Greek guerillas--a rather baffling police operation executed by indigenous forces, with the United States supplying only material aid and technical advice. Nineteen forty-nine was the year that turned the tide in Berlin††through a massive logistic effort carried out primarily by the Americans themselves. The current year has seen United Nations intervention in Korea, again an operation in which American forces have played the leading role. These examples suggest that the number of active danger spots at any one time is limited, and that it is possible to shift the emphasis and to divert resources from one place to another nearly as rapidly as the Soviet Union can itself shift its point of attack. The resources, the technique, perhaps some of the same planes that won the struggle from Berlin went into the air movements of troops and supplies that contributed so decisively to the American advance in Korea. In sum, the containment policy rests on the idea of a strategic reserve--a flexible concept as opposed to the static and impossible notion of simply manning a wall.