Why has South Korea long been heralded as a Christian "success story" when only about 30 percent of its population identifies as Christian? Forging Protestant Allies shows that the popularization of South Korea's image as a Protestant stronghold took shape during the Korean War.As the conflict unfolded, mission societies and faith-based aid agencies in the United States sought to overcome American indifference toward a distant and unfamiliar country. To mobilize sympathy and support, they reimagined South Korea as a Christian ally on the front lines of the global struggle against communism. In this context, "forging" operated in two distinct ways. First, the war fostered new partnerships: not only between Korean churches and Western Protestant organizations, but also among the many mission boards, denominational agencies, and ecumenical relief groups that converged on the peninsula. These collaborations were real and often consequential. But "forging" also captures a second process^—^crafting an appearance of unity that belied realities on the ground. Mission societies and aid agencies emphasized shared purpose while downplaying substantive theological disagreements, institutional rivalries, and persistent hierarchies of race, nation, and power. In this dual sense the book traces how the idea of a unified Protestant front in Korea was forged.Drawing on extensive archival research conducted across four continents, Forging Protestant Allies uncovers the tensions beneath proclamations of unity. It follows how mission societies negotiated jurisdictional boundaries, how mainline and evangelical agencies contested the purpose of aid, and^—^crucially^—^how Korean Christian leaders leveraged this Cold War attention to challenge missionary hierarchies, break old alliances, and forge new transnational partnerships on their own terms.