The May 1926 Coup D'etat in Poland inaugurated what has become known as the period of sanacja or ""cleansing."" The event has been explored in terms of the impact that it had on state structures and political styles. But for both supporters and opponents of the post-May regime, the sanacja was a catalyst for debate about Polish national identity, about citizenship and responsibility to the nation, and about postwar sexual morality and modern gender identities. ""The Clash of Moral Nations"" is a study of the political culture of interwar Poland, as reflected in and by the coup. Eva Plach shifts the focus from strictly political contexts and examines instead the sanacja's open-ended and malleable language of purification, rebirth, and moral regeneration. In tracking the diverse appropriations and manipulations of the sanacja concept, Plach relies on a wide variety of texts, including the press of the period, the personal and professional papers of notable interwar women activists, and the official records of pro-sanacja organizations, such as the Women's Union for Citizenship Work. ""The Clash of Moral Nations"" introduces an important cultural and gendered dimension to understandings of national and political identity in interwar Poland.