The six countries of Northeast Asia are led by leaders known for their assertiveness. This forum excludes the two who are most bellicose: Vladimir Putin and Kim Jong-un. Despite some claims at times that they could be swayed to make a deal, their inclination to resort to provocations is no longer in doubt. Abe Shinzo spent years wooing Putin in the hope that he would forsake a threatening posture. Moon Jae-in devoted his foreign policy in 2018-19 to trying to persuade Kim that he could gain stability and prosperity by agreeing to denuclearize. Now, it can only be assumed that both Putin and Kim will eschew a pathway to regional cooperation unless they are successful in their far-reaching geopolitical objectives. That leaves the other four leaders in the Northeast Asian diplomatic caldron challenged to work together or go their separate ways. Given their own assertiveness, coordination is proving difficult. All four—Xi Jinping, Donald Trump, Abe Shinzo, and Moon Jae-in—have striven to transform the regional order, and today, in the face of a region being pushed toward confrontation, must decide how vigorously to proceed. It is their recent assertiveness that is the shared subject covered in the following four articles.