The ROK-U.S. alliance is an Indo-Pacific alliance. The first sentence of the ROK Strategy for a Free, Peaceful, and Prosperous Indo-Pacific Region states “The Republic of Korea is an Indo-Pacific Nation.” The U.S. Indo-Pacific Strategy begins by stating, “The United States is an Indo-Pacific power.” In their first summit meeting, President Yoon and President Biden agreed to develop ROK- U.S. into a global comprehensive strategic alliance. Moreover, the two leaders emphasized that preserving peace and stability in the Taiwan Strait is a significant component of security and prosperity for the Indo-Pacific region. If China attacks Taiwan, the United States would probably send forces to protect Taiwan. This research discusses ROK’s possible policy options and the issues that should be considered under the circumstances. Put simply, ROK’s policy options will be limited due to its security situation on the Korean Peninsula. In this regard, it would be critical for the allies to discuss and prepare for the contingencies that may appear in the Taiwan Strait.