Neither the unanimous decision by the Permanent Court of Arbitration in The Hague, nor China’s rejection of it, was surprising. The timing of it was, however, as serendipitous as China’s rejection is ominous. Coming as Republican delegates convene on Lake Erie’s shore, the tribunal’s opinion about the South China Sea underscores the current frivolousness of American politics, which is fixated on a fictitious wall that will never exist but silent about realities on and above the waters that now are the world’s most dangerous cockpit of national rivalries.

China’s “nine-dash line” aggression — asserting sovereignty over the South China Sea — is being steadily implemented by the manufacture and militarization of artificial “islands” far from China’s mainland, and by increasingly reckless air and naval actions in the region. China is attempting to intimidate the six nations (the Philippines, Taiwan, Vietnam, Brunei, Malaysia and Indonesia) whose claims conflict with China’s. China has threatened these nations’, and others’, freedom on the seas, fishing rights, oil exploration and more.

In 2013, the Philippines took its case to the Court of Arbitration, whose jurisdiction China pre-emptively rejected. The Philippines has now won most of its claims but has achieved nothing unless the United States leads regional powers in enforcing this decision. The Hague has no navy.

International law fulfills important functions but often is most successful when least important: It arbitrates disputes about rights and duties among likeminded nations that acknowledge its underlying norms. When, however, a rising nation’s interests and aspirations conflict with those norms, trying to restrain this nation with those norms is like lassoing a locomotive with a cobweb.

So, although it was prudent for the Philippines to bring this case, and although the court conscientiously measured China’s claims and behavior next to the pertinent precedents, the court’s correct legal decision makes the world more dangerous: China now knows that only force can achieve its ends. We are, as Secretary of Defense Ash Carter has said with notable understatement, in a “long-term competitive situation.”

The projection of U.S. power to the far side of the Pacific depends on alliances and cooperation — including access to bases — with Australia, India, the Philippines, Thailand, Japan, South Korea and others. China’s aim of dominance in the region can only be achieved by weakening the U.S. allies’ confidence — particularly that of the Philippines, which seems susceptible to China’s promises of development projects — in U.S. resolve. And confidence in U.S. skill at calibrating the pressure requisite for countering China’s ambitions without provoking a Chinese miscalculation in a region where U.S. military assets, especially naval, still dominate.

Two U.S. carrier groups have visited the region this year. China is developing and deploying a modern nuclear submarine fleet, land-based aircraft and anti-ship ballistic missiles, and other means of pushing back the U.S. presence. Chinese military aircraft have made dangerous approaches to U.S. military aircraft. A Taiwanese naval vessel accidentally sank, with an anti-ship missile, a Taiwanese shrimp boat. Accidents happen. And intentional acts can have unintended consequences. A single assassination loosed the cascade of events that produced the war that was devouring Europe 100 years ago.

At the start of the turn of the 20th century, the world’s most formidable challenge was to integrate into the international system a rising, restless, assertive Germany. This did not go well. Early in the 21st century, China poses a comparable challenge. If this does not go well, the differences might be arbitrated by weapons undreamt of a century ago.

This week, the Republican Party will formalize its judgment that the Navy, the nuclear launch codes and other important things should be placed in the hands of someone not known for nuance, patience or interest in allies and collective security. Americans, dismayed by two consecutive commanders in chief — the recklessness of one and the inconstancy of his successor — must now decide whether, and if so how and by whom, they want U.S. power to be projected.

In the South China Sea, says Secretary Carter, America must steel itself for “a long campaign of firmness, and gentle but strong pushback.” This will require freedom of navigation assertions, involving naval and air operations that challenge, among other things, China’s expansive claims to sovereignty over islands and waters far from its mainland.

If the next president does not conduct such operations with steady, measured skill, the result could be the collapse of America’s position in the world’s most populous, dynamic and perhaps dangerous region, or war. Is any of this on anyone’s mind in Cleveland?

© 2016, Washington Post Writers Group