This paper explores the politics surrounding the dismantling of the ruins of Nagasaki's Urakami Cathedral. It shows how U.S-Japan relations in the mid-1950s shaped the 1958 decision by the Catholic community of Urakami to dismantle and subsequently to reconstruct the ruins. The paper also assesses the significance of the struggle over the ruins of the Urakami Cathedral for understanding the respective responses to atomic bombing of Hiroshima and Nagasaki. It further casts new light on the wartime role of the Catholic Church and of Nagai Takashi.