Can a state be a credibly ally and still partner closely with its rival? During the Cold War, no country was allied to one side and strategically tied to the other; it may have accommodated the rival to a degree, but this fell short of any actual aligning behavior. Today, in what is now frequently referred to as the “new cold war,”1 some question whether states are exhibiting similar tendencies. I argue South Korea provides new, albeit preliminary, insights in this respect: its alliance with the United States—though under various strains—has remained resilient even as South Korea’s ties to China have deepened and the US-China relations have deteriorated. Indeed, this strategy of “double allegiance” is distinctive, even if it is unlikely to sustain over the long run.