This paper focuses on the fact that two bilateral agreements (UK-Japan and US-Japan) concerning the peaceful use of nuclear energy were concluded on the same day, June 16, 1958. Why did Japan and the UK conclude such an agreement, which entailed the risk of deteriorating their relationship with the US, as the agreement clearly obstructed the US’s Cold War strategy? Why and how were these two agreements concluded on the same day? I try to answer these questions by scrutinizing the diplomatic records.

The first section reveals that Japan approached the UK regarding the possibility of cooperation in the fall of 1955, mainly to avoid sole dependence on the US. On the other hand, the UK approached Japan not only regarding the economic matter of exporting its nuclear reactors but also regarding political interests, such as the restoration of its status as a great world power. The author suggests that for the UK and Japan, their agreement was a means of seeking autonomous foreign policy, independent from the US.

However, as the second section shows, the US began to intervene with both countries and succeeded in diminishing their eagerness for the agreement. The UK and Japan decided to place the highest priority on recovering and enhancing their relationship with the US. The preliminary negotiations between the UK and Japan began in September 1957, but they would soon be stuck due to their distrust for each other.

The third section was an analysis of the process of two bilateral agreements that were concluded on the same day. The US-Japan negotiations began in January 1958 and quickly reached a provisional signature on April 28. The US and Japan also planned to reach the formal signature on May 27; however, it was postponed for various reasons. Although the UK-Japan negotiation was finalized on May 20, both countries had lost their eagerness for cooperation, and neither could find a reason to rush to signature. Therefore, Japan took the initiative to adjust the two agreements so that they were concluded on the same day, June 16, 1958.

Finally, this paper points out that the outcome of the UK-Japan bilateral agreement was not expected before the negotiation; however, both countries achieved their political agendas with the US soon after the date of the signature. By considering these processes, the author concluded that the original goal of autonomous foreign policy shifted to limited or partial autonomous foreign policy, which was subordinated to the U.S.-led Cold War system.