This paper analyses the Holy See's diplomatic and doctrinal response to the People's Republic of China through a sequential examination of three pivotal public pronouncements: the 1952 Apostolic Letter Cupimus Imprimis, the 1954 encyclical Ad Sinarum Gentem, and the 1958 encyclical Ad Apostolorum Principis. Cupimus Imprimis (1952) established the initial public narrative. Addressed to the Chinese faithful, this letter performed a significant diplomatic function by asserting the Church's cultural and spiritual compatibility with the Chinese people while reinforcing the necessity of ecclesiastical loyalty to the Roman Pontiff. Ad Sinarum Gentem (1954) marked a strategic shift in response to the nascent Catholic Patriotic Association (CPA). This encyclical transformed pastoral solidarity into a formal doctrinal manifesto, explicitly challenging the CPA's principles and the state's ideological requirements. Finally, Ad Apostolorum Principis (1958) represents a definitive diplomatic rupture. Responding to the unauthorised consecration of bishops, this document provided a comprehensive canonical censure, formally invalidating the state-sanctioned church structure. Collectively, these documents served as the primary instruments of Vatican statecraft in the absence of formal diplomatic channels. This paper posits that their progression, from pastoral appeal to doctrinal defence and, ultimately, to canonical censure, demonstrates Pius XII's systematic use of the papal magisterium to engage in global geopolitical discourse. This strategy aimed to define ideological boundaries, challenge the international standing of the Beijing administration, and assert universal papal jurisdiction, exemplifying the utility of public doctrine as a core component of the Holy See's soft-power diplomacy.