Many politicians have recently voiced concern regarding Chinese activity in the South China Sea. With all the issues to be discussed, some might wonder why so much attention has been paid to a body of water so far away from the U.S.

The answer lies in an American interest as old as the Republic itself.

It is not easy to trace the forces that shape the history of a nation’s interest. It is undeniable, however, that the freedom of the seas is among the most an enduring of America’s. In fact, concern for it brought us to blows with the British as early as 1812.

The U.S. interest resides in the principle because we know that whatever the circumstances, freedom of the seas will serve us, and our allies, well. When the principle is respected, people of sovereign nations can trade with one another by sea unhindered and to their great benefit.

The South China Sea may be on the other side of the Pacific. But it is a major thoroughfare for trade. As pointed out in The Heritage Foundation’s “2016 Index of U.S. Military Strength,” roughly half of global trade in goods, a third of trade in oil, and over half of global liquefied natural gas shipments pass though the South China Sea.” In an global economy where the market is the most powerful arbiter in deciding how production is distributed, and where market disruptions in one part of the world can directly impact matters as close to home as retirement accounts invested on Wall Street, the free flow of trade is of enormous importance to American citizens.

For this reason, freedom of the seas is not just something Republicans are concerned about. Disagree with the way President Obama is pursuing our interest in it, or with the cuts in military spending that have handicapped our ability to protect it, but it is certainly something he is focused on.

In fact, the American president has just returned from meetings in Manila and Kuala Lumpur, where he raised the issue quite pointedly. The problem for the U.S. today is the People’s Republic of China and the massive claim it stakes to the virtually the entire sea.

Their claim to the waters of the South China Sea is comparable to a U.S. claim on the entire Gulf of Mexico, or all the water between the lower 48 and Hawaii. It cannot go unchallenged unless the U.S. and the rest of the world want to ply those waters as guests of the Chinese.

Their claim to the waters of the South China Sea is comparable to a U.S. claim on the entire Gulf of Mexico

That is the expressed Chinese preference, and they are correct that commercial shipping is not threatened today. The catch is that if the ships are mere guests, then, like all guests, they may also be asked one day to go home, or otherwise have conditions placed on their presence.

The way to protect American interests in the free flow of commerce over the long term is not to entrust it to the good graces of the Chinese, but to enshrine and defend the principle at stake.

Defense of principle raises another connection to U.S. interest in freedom of the seas. The U.S. has a number of treaty commitments in the Western Pacific and a quasi-guarantee for Taiwan’s security. If it is ever called to come to the defense of South Korea from the madman in Pyongyang or to the defense of Taiwan—which, despite warming relations, the Chinese remain focused on like a laser—the U.S. absolutely must be able to transit those waters. And we need to exercise there today in the event that, God forbid, war does break out.

The U.S. Navy fought its way through the Pacific in the 1940s at great cost to American lives. In the long run, it is much less costly to defend our right to be there today than prove the point by force of arms later.

As far away as it may seem, the ability of the U.S. and other nations to freely exercise their rights in the South China Sea could mean the difference between war and peace and our continued prosperity here at home. It is a good thing that Republican candidates and Obama are so focused on it.