A Sacred Oath: Memoirs of a Secretary of Defense During Extraordinary Times – An Instant New York Times Bestseller: A Pentagon Insider's Tumultuous Years Under President Trump

by Mark T. Esper

Another major issue, which began in 2018 and bubbled over in the summer of 2019, was the deteriorating relationship between South Korea and Japan, and the effect it had on our collective deterrence in the region. It was frustrating to see these two long-standing allies of ours squabbling between themselves as North Korea tested ballistic missiles and developed nuclear weapons. Meanwhile, Beijing went about flexing its muscles in the waters of the East China Sea and beyond. Even Russia benefited from this dispute. Domestic politics prevented Seoul from containing the matter—the result of a long and horrible history—and impacted the ability of the United States, Korea, and Japan to work more closely together to improve our collective security.