Because geopolitics is based on the eternal verities of geography, relatively little in geopolitics comes to an end. The Warsaw Pact may have dissolved following the collapse of the Berlin Wall, but Russia is still big and it still lies next door to Central and Eastern Europe, so a Russian threat to Europe still exists. Japan may have been defeated and flattened by the U.S. military in World War II, but its dynamic population -- the gift of a temperate zone climate -- still projects power in the Pacific Basin and may do so even more in the years to come. The United States may have committed one blunder after another in Vietnam, Iraq and Afghanistan, yet through all of these misbegotten wars the United States remains by a yawning margin the greatest military power on earth -- the gift, ultimately, of America being a virtual island nation of continental proportions, as well as the last resource-rich swath of the temperate zone to be settled at the time of the European Enlightenment.

So we come to the Middle East, which, despite all its changes and upheavals in the course of the decades and all the prognostications of a U.S. "pivot" to the Pacific, remains vital to the United States. Israel is a de facto strategic ally of the United States and for over six decades now has remained embattled, necessitating American protection. The Persian Gulf region is still the hydrocarbon capital of the world and thus a premier American interest. Certainly, officials in Washington would like to shift focus to the Pacific, but the Middle East simply won't allow that to happen.

And yet there is an ongoing evolution in America's relationship with the region, and attrition of the same can add up to big change.

For decades the Persian Gulf represented a primary American interest: a place that was crucial to the well-being of the American economy. The American economy is the great oil and automotive economy of the modern age, with interstate highways the principal transport link for an entire continent. And Persian Gulf oil was a key to that enterprise. But increasingly the Persian Gulf represents only a secondary interest to the United States: a region important to the well-being of American allies, to be sure, and to world trade and the world economic system in general, but not specifically crucial to America itself, the war to defeat the Islamic State notwithstanding. However much oil the United States is still importing from the Persian Gulf, the fact is that America will have more energy alternatives at home and abroad in future decades.

Indeed, the United States is on the brink of being, in some sense, energy self-sufficient within Greater North America, from the tar sands of Alberta, Canada, to the oil fields of Venezuela. U.S. President Barack Obama may veto the Keystone Pipeline System that would bring oil from Canada to the Gulf of Mexico, but industry experts believe that the future will in any case see continued cooperation between the United States and Canada in the energy sector. There is, too, the vast exploitation of shale gas in Texas, Louisiana, North Dakota, Ohio, Pennsylvania and New York. U.S. companies will, in addition, probably be investing more in the Mexican and (eventually) Venezuelan energy industries in the future, following increasing economic liberalization in Mexico City and the possible, eventual passing of the Chavista era in Caracas. All this serves to separate the United States from the Middle East.

While the United States will have less and less need of Middle East hydrocarbons, the Middle East will for years to come be consumed by internal political chaos that itself exposes the limits of American power. In the era of strong authoritarian Arab states, American power was easy to project. It was just a matter of U.S. diplomats brokering peace treaties, separation of forces agreements, secret understandings, and the establishment of diplomatic relations between Israel and some of its neighbors. After all, Egypt, Syria, Jordan and other Arab countries all had just one phone number to call -- that of the dictator or monarch in charge. But whom do you phone now in Tripoli or Sanaa or Damascus (even if Cairo is temporarily back under military dictatorship)? With no one really in charge, it is harder to bring American pressure to bear. Chaos in and of itself stymies U.S. power.

The United States remains a global behemoth. And U.S. power, particularly military power, can accomplish many things. The United States can defend Japan and Taiwan against China, South Korea against North Korea, Poland against Russia, and ultimately Israel against Iran. But one thing American power cannot accomplish, as a decade in Iraq and Afghanistan showed, is to rebuild complex Islamic societies from within. And rebuilding societies from within will be the fundamental challenge faced by the Arab world for at least the next half-decade. Thus, America, in spite of its latest military intervention, becomes less relevant to the region even as the region itself no longer represents quite the primary interest to America that it used to. We should keep this in mind now that the war against the Islamic State threatens to distract us from other theaters.

So in the glacial changes that often define geopolitics, the United States (that is, Greater North America) is moving away from the Middle East. This occurs as the Middle East itself slowly dissolves into a Greater Indian Ocean world.

For as the United States requires fewer and fewer hydrocarbons from the Middle East, China and India require more and more. Their economies may have slowed, but they are still growing. The Persian Gulf can -- in the final analysis -- erupt into a nuclear firestorm and America will survive well, thank you. But China and India will have the greater problem. China does not have a foreign policy so much as a resource-acquisition policy. Not only is it increasingly involved in energy deals with Saudi Arabia, Iraq and Iran, but China is currently trying to build, run or help finance container ports in Tanzania and Pakistan in order to eventually transport both commercial goods from the western rim of the Indian Ocean to the eastern rim and on into China itself. And while all this is happening, Oman, for example, plans to build routes and pipelines from outside the Strait of Hormuz to countries inside the strait, even as China and India have visionary plans to link energy-rich and landlocked Central Asia by pipeline to both western China and the Indian Ocean.

In this evolving strategic geography of the early- and mid-21st century, the Middle East slowly becomes a world defined less by its own conflict and trading system and more by a conflict and trading system that spans the whole navigable southern rimland of the Eurasian supercontinent, with tentacles reaching north into Central Asia. The Indian Ocean thus emerges as the global hydrocarbon interstate linking the oil and gas fields of the Persian Gulf with the urban middle class concentrations of the Indian subcontinent and East Asia.

In such a scenario, the United States does not desert the Middle East, just as China and India do not greatly infiltrate it. But there is movement -- especially psychological -- away from one reality and toward another. And in the process, the Middle East as a clearly defined region of 20th century area studies means less than it used to.

Boiled down to the current newspaper headlines, Obama has not been irresponsible by refusing to get more involved than he has in the sectarian chaos of Syria and deciding for so long to withhold military action against Iran's nuclear facilities. His presidency is simply a sign of the times: a sign of the limits of U.S. power and of the more limited interests the United States has in the Middle East, terrorism excepted. The opening to Iran, as demonstrated by the interim agreement concerning Tehran's nuclear program, is part of this shift. The United States is trying to put its house in order in the Middle East through a rapprochement of sorts with the mullahs so that it can devote more time to other regions. Of course, this has been upended by the war against the Islamic State. But it will remain an overriding American goal nevertheless.