[1][2] The name of the protests comes from the Japanese term for "Security Treaty," which is Anzen Hoshō Jōyaku (安全保障条約), or just Anpo (安保) for short.

[4] In the aftermath of this incident, a planned visit to Japan by United States president Dwight D. Eisenhower was cancelled, and conservative prime minister Nobusuke Kishi was forced to resign.

[12] The United States agreed to a revision, negotiations began in 1958, and the new treaty was signed by Eisenhower and Kishi at a ceremony in Washington, DC, on January 19, 1960.

[19] This victory emboldened the protestors, and rather than disbanding, the anti-Police Bill coalition remained active and recruited new member organizations to oppose the revised Security Treaty, which was in the final stages of negotiation.

[21][22] Over the rest of 1959 and into 1960, the protest movement continued to gradually grow larger, especially as heightening Cold War tensions inspired fear that the new treaty would lock Japan into one side of a dangerous global conflict.

[13] In the aftermath of the incident, the Soviet Union disinvited Eisenhower from his planned visit to the USSR the coming summer and the brief thaw in the Cold War came to an end.

[24] Late in the evening on May 19, Kishi took the desperate measure of suddenly and unexpectedly calling for a 50-day extension of the Diet session, in defiance of longstanding parliamentary norms and over the opposition of many members of his own ruling Liberal Democratic Party (LDP).

With only members of Kishi's own party present, the revised Security Treaty was approved by the Lower House of the Diet with no debate and only a voice vote.

[33] The police finally succeeded in clearing the Diet compound after 1 a.m., but in the struggle, a young female Tokyo University student and Zengakuren member named Michiko Kanba was killed.

[35] However, he was talked out of these extreme measures by his cabinet, and thereafter had no choice but to cancel Eisenhower's visit and take responsibility for the chaos by announcing his own resignation on June 16.

[34] On June 17, newspapers across the nation, which had previously supported the protestors in their struggle to oust Kishi, issued a joint editorial condemning violence on both sides and calling for an end to the protest movement.

[37] The 1960 Anpo protests had ultimately failed to stop the revised US-Japan Security Treaty from taking effect, but they did force the resignation of the Kishi Cabinet and the cancellation of Eisenhower's planned visit.

Kishi was succeeded as prime minister by Hayato Ikeda, who took a much more conciliatory stance toward the political opposition, indefinitely shelved Kishi's plans to revise the Japanese Constitution, and announced the Income Doubling Plan to redirect the nation's energies away from contentious political struggles and toward a nationwide drive for rapid economic growth.

[38] The anti-American aspect of the protests and the humiliating cancellation of Eisenhower's visit brought US-Japan relations to their lowest ebb since the end of World War II.

[41] In Japan, the protests spurred a new wave of right-wing activism and violence, including the assassination of Socialist Party chairman Inejirō Asanuma during a televised election debate in the fall of 1960.

[42] Asanuma's assassination weakened the JSP,[43] which was further riven by conflicts over the conduct of the anti-Treaty protests, leading to the splitting off of the breakaway Democratic Socialist Party.

[49] However, prime minister Eisaku Satō (who was Kishi's younger brother) opted to ignore the protests completely and allow the treaty to automatically renew.