The postwar US-Japan security relationship is one that emerged very quickly in the immediate postwar period, but also quite unexpectedly. SCAP, the American occupation government, initially saw the end game for Japan was a demilitarized polity that would delegate security issues to the US. For its part, the emerging Japanese civilian government under the conservative LDP politician PM Yoshida Shigeru pursued its own agenda which intersected with American strategic thought in the evolving Cold War. This partnership though was not entirely free of complications and neither side truly got what they wanted out of their ally.

"Formless" is the best word to describe American strategic thought with regards to Japan's immediate geopolitical future in the Autumn of 1945. SCAP generally did not envision reforming Japan with an eye to meet American needs. Article 9 in the Japanese Constitution outlawed war as a policy and there was a good deal of SCAP directives aimed at the demilitarization of Japanese society and culture. This was in keeping with much of the wartime planning for East Asia was predicated on both having a Nationalist China as well as Commonwealth forces form a bulwark for US interests, especially as the Cold War started to shape up. Events in China with the resumption of the Civil War as well as the general draw down of the British East of Suez almost immediately meant that the US was lacking a regional power partner in East Asia. This did not mean that American planners immediately considered Japan as the nation that could fill this vacuum. As late March 1949, SCAP chief MacArthur claimed in a newspaper interview that :

Japan should be the Switzerland of the Far East and neutral for the same reasons Switzerland is neutral- no matter which side she might join, she would inevitably be destroyed.

Pace MacArthur's public statements, both the State Department and the Pentagon were considering rearming Japan and having it as the central regional partner.

It took the twin shocks of the victory of the Communists in China and the Korean War to transform these thoughts into action. The latter conflict opened up the frightening possibility that Japan could be invaded and the overstretched US forces would be unable to defend the islands. The Korean invasion alarmed the Japanese government as well and it led to the expansion of the National Police Reserve (NPR), a sort of ersatz military that the US armed with a variety of weapons.

The NPR laid the foundations for the later Self-Defense Forces (SDF), but it was not a straight line. Yoshida pursued what later be known as the Yoshida Doctrine, in which the Japanese government would prioritize economic growth while relying upon US power for security. The role Yoshida envisioned for the SDF was one that would supplement the American defense network in Japan. Yoshida had both domestic and international motives for this limited commitment. Domestically, an open move against Article 9 would provide fuel for his left-wing opponents in the Diet. Moreover, Yoshida also recognized that economic growth was also more important for immediate domestic needs. And like his German counterpart Adenauer, Yoshida was adamant that civilian control over the military was essential. As one of the sidelined bureaucrats from the wartime government, Yoshida came from a political milieu that looked askance at militarist rule, especially given the scale of the defeat in 1945. Internationally, Yoshida also recognized that the US arguably needed Japanese bases and its geographic position far more than the US needed Japan to make a costly outlay for rearmament. This was one of the key differences between Yoshida and Adenauer as the German Chancellor and a number of his CDU-CSU allies were more leery of American commitments to West German defense.

Thus although the common metaphor of the US-Japanese relationship was spear and shield- with the US able to strike out offensively while the SDF guarded US bases-the reality was often more complicated than such a symbiotic metaphor. Pentagon estimates in the late 1950s and early 1950s evaluated the SDF as a credible deterence to the Soviets, but not a force that could either project power abroad or be able to stop a Soviet invasion of Hokkaido if the Soviets pressed them. For these reasons, Washington often considered Japanese rearmament tardy and never as thorough to meet the needs of the Cold War in East Asia, despite the US sighning Mutual Cooperation Treaties with Japan in 1952, 1960, and 1970. The escalation of the Vietnam War put a further strain on the US-Japanese relationship as both the Johnson and Nixon administrations expected Japan to act as a regional ally and send troops to South Vietnam as its other allies, South Korea and Australia. This was an issue which Tokyo would not budge on, and earned Japan a good deal of resentment in the US during the 1970s. Kissinger in particular was quite vocal in private with his deriding of the Japanese, at one point calling his Tokyo counterparts "small and petty bookkeepers." Such opprobrium was not limited to the corridors of power in the US as the declining American economy of the 1970s fueled resentment that Japan was profiting off of US defenses by not maintaining an army and instead investing the monies it would have used on defense into automobile and consumer electronics industries.

Such complaints, which only grew during the Japan-bashing of the 1980s, were more than a tad unfair. Japan, despite its foot-dragging, was rearming and building up its own domestic arms industry, which was not only time-consuming, but expensive. The threat of a wide-scale US post-Vietnam drawdown in the region also forced a greater commitment on Tokyo's part to beef up the SDF. Although the naval and air components of the SDF had practiced joint operations with the US in the 1960s, the ground forces started to so in the 1970s. There was a fear within Tokyo that the Vietnam defeat, coupled with the domestic problems in South Korea during the Park dictatorship could have led to a domino effect in which Japan was isolated in the region. The Belenko MiG-25 defection also added urgency to defense expenditures as fears of Soviet retaliation or a commando raid to destroy the plane did concern SDF chiefs. One of the ironies of the 1980s was that despite the Japan-bashing tone of US domestic politics, the US-Japanese security arrangement was the closest it had ever been to reaching the shield-sword metaphor. The Japanese significantly expanded their air defense and ASW forces and the Japanese PM Suzuki in May 1981 actually called the bilateral relationship a military alliance.

Suzuki's breaking of this taboo in 1981 underscores the real domestic costs of the Yoshida Doctrine and its various post-Yoshida iterations. In short, the alliance put the LDP in a very awkward position. While the Japanese nationalist right was staunchly anti-communist, ideologues like Ishihara Shintaro exoriated the mainstream LDP champions of the alliance as the lap-dogs of American power. This disgruntlement sometimes exploded into violence, such as the assassination of the left-wing politican Asanuma Inejiro by a right-wing nationalist on national tv or the seppuku of the author Mishima Yukio after his private army tried to take over a SDF military base. Such events, which were widely publicized around the world- the photo of Asanuma's assassination won a Pulitzer- created an embarrassing situation for the LDP. From the perspective of the Japanese left, this security arrangement was Japan being coopted by American imperialism and militarism. While the extremes of left-wing disgruntlement likewise manifested itself in the terrorism like the Japanese Red Army on the extremes, there was always a danger that the Social Democratic Party could use the sotto voce US alliance as a wedge issue to unseat the LDP and unify the splinter-prone Japanese left. Adding to this, the presence of American forces and bases was incredibly unpopular within Japan. The transformation of Okinawa into a hive network of American bases, the perceived footdragging of US military justice to punish crimes committed on Japanese soil, the association of US bases with vices like prostitution and drugs, as well as the extreme unpopularity of the Vietnam conflict within a broad spectrum of the Japanese electorate also made the alliance a political liability for the ruling governments.

Although the mechanisms of the alliance were at their most functional in the 1980s, there were rumblings in political quarters that the alliance needed to change. Suzuki's successor, Nakasone Yasuhiro struck a more militant line versus the Soviets than his predecessors. While such a stance indicated a success for the alliance, it was also a sign that Japan was making tentative steps away from the Yoshida Doctrine's subservient position accorded to Japan. Greater stridency also indicated that Japan could toe an independent line and Gorbachev and his Foreign Ministry began to hold out the prospect of returning the Kuriles and a formal peace treaty with Japan. These feelers foundered for a number of reasons, not the least of which was still the importance of the alliance for Japan, but the fact that the Soviets made them suggests the new vulnerabilities of the alliance in the bubble economy.