After disposing of the North Korean nuclear program, Trump quickly turned his attention to China, whom he had identified as his principal adversary. While the ostensible cause for concern was the fill islands, the real issue, in his eyes, was the trade deficit, although he had no realistic ideas on how to address it.
The crisis started when Trump, without warning, announced a blockade of the fill islands. The Chinese leadership, believing that time was on their side, did not relish the thought of a confrontation with the US, but, with emotions running high on the internet, felt obligated to choreograph a response. For his part, Trump sent a private message to Beijing to the effect that what he really wanted to do was to talk about trade.
The world watched in horror as Chinese ships attempted to ram American vessels and used water cannon to try to break the blockade. The two nuclear powers appeared to be on the verge of a shooting war. Neither side used lethal force, however, and the war was averted.
In the end, the issue was apparently resolved when Trump lifted the blockade and agreed to stop sending weapons to Taiwan in exchange for quotas on a variety of imported goods. In keeping with his usual practice, however, Trump privately promised the Taiwanese government that he would ignore his written commitments and continue the arms sales. The Chinese government, no strangers to cheating, had anticipated this and nullified the effect of the import quotas simply by selling through middlemen from other countries.
The crisis accomplished nothing. America was blamed for it throughout the world, and was universally viewed as a rogue nation. American prestige had never been lower. From all appearances, Trump did not care.