米国の同盟政策における核兵器の位置づけの変容

――核兵器共有と一九六六年ＮＡＴＯ危機――

抄録

How do alliance partners treat the problem of credibility of extended deterrence when they understand seriousness of security threats differently? Do they continue negotiations on the measures to confirm credibility? If so, why? To study this problem, this paper examines US policies toward nuclear sharing when France challenged NATO and shook US-European relations since World War II.

France withdrew from the military organization of NATO when nuclear sharing and the stationing costs of the US/British troops on the European continent also troubled the alliance. The administration of Lyndon B. Johnson treated them as parts of a large problem. Washington also tried to solve these related problems through closer cooperation of the United States, the British, and the West Germans. This tripartitism (or trilateralism) was the basic framework through which the Johnson administration considered the ways to deal with individual problems in NATO.

Nuclear sharing was not only a part of tripartitism but also a means to promote it. At least by the end of 1964, the respective US governments regarded nuclear sharing as the major way to secure credibility of extended deterrence and, as a result, to hold the alliance together. This attitude changed, however, by the beginning of 1966 when the Johnson administration seriously studied the France-NATO problem and the troop stationing costs. By constructing a nuclear consultation mechanism based on US-UK-FRG cooperation, Washington expected to introduce tripartitism into NATO.

The problem of the US/British troop stationing costs grew tense in the middle of the same year. The Johnson administration tried to persuade Bonn to bear more costs of these costs, and this burden-sharing was expected to be a part of tripartitism. Washington tried to introduce a burden-sharing mechanism into NATO in face of the French challenge. President Johnson particularly considered a deal with Bonn over nuclear sharing and the troop costs problem, and this became clear in unofficial US-Soviet talks over the Non-Proliferation Treaty. Johnson insisted on sustaining the possibility of a common strategic nuclear force despite Soviet rejection of any common strategic nuclear force with FRG participation. Here Johnson expected to open this option of a common nuclear force to encourage Bonn’s acceptance of larger burden to support US/British forces.

This paper shows that a nuclear sharing measure played a role in inter-allies’ negotiations even though its prime purpose, securing credibility of US extended deterrence, grew less relevant. This perspective could enhance our understanding of nuclear issues under a less tense international situation.