With U.S.-North Korea talks at an impasse and Pyongyang sticking to a tactically ambiguous line, attention has moved away from the Korean Peninsula. However, policymakers should not lose sight of ongoing developments within the U.S.-South Korea alliance. Although the Trump administration refers to the alliance as the “linchpin” of its Indo-Pacific strategy, and Congress passes resolutions in support of Asian allies, it is unclear whether U.S. policymakers fully appreciate the extent to which U.S. and South Korean perspectives diverge on fundamental bilateral and strategic issues.

Whether or not diplomacy with Pyongyang moves forward or continues to erode, alliance cohesion is crucial. Yet the allies face multiple interrelated challenges, which not only undermine cohesion vis-à-vis Pyongyang, but call into question the longevity of the alliance itself. These include tensions over the nature and scope of alliance cost-sharing; changes to the alliance’s bilateral military command architecture; and, more broadly, differing perspectives amid a shifting strategic context and rising China.

SMA Talks

Washington requesting that Seoul take on a larger share of the alliance burden is nothing new. Such requests began in the 1960s and became more institutionalized in the late 1980s amid the first Special Measures Agreement (SMA) negotiations. What is different today is the nature and extent of President Donald Trump’s demands.

As a recent retrospective analysis shows, Trump’s skepticism about the alliance or need for U.S. forces on the Korean Peninsula is actually quite consistent. It long preceded his presidency. Immediately upon arrival, Trump essentially blew up the established SMA process. He derided Seoul as a free-rider, and claimed Washington gets “practically nothing compared to the cost” of the alliance...