Senator James Webb’s recent op-ed in the Wall Street Journal constitutes a powerful warning to the man who will occupy the White House Oval Office after January’s inauguration day, whether he is President Obama in a second term or Republican challenger Mitt Romney in a first term. Webb, the Virginia Democrat who will relinquish his Senate seat after November’s election, called attention to China’s ever growing aggressiveness in laying claim to vast and far-flung areas of Asia, including 200 islands (in many instances mere “islets” of uninhabited but strategically significant rock) and two million square kilometers of water.

“For all practical purposes,” writes Webb, “China has unilaterally decided to annex an area that extends eastward from the East Asian mainland as far as the Philippines, and nearly as far south as the Strait of Malacca.” This huge territorial claim, which includes nearly the entire South China Sea, clashes with territorial claims of China’s neighbors in the region, including Vietnam, Japan and the Philippines. Brushing aside these counter-claims, China has created a new administrative “prefecture,” called “Sansha,” with headquarters in the Paracel Islands and lines of authority that go directly to the central government in Beijing.

The Paracels are more than 200 miles southeast of China’s southernmost point of territory, and for decades Vietnam vehemently has claimed sovereignty over them. But now they will house offices for 45 Chinese legislators appointed to administer the new prefecture, along with a 15-member Standing Committee, a mayor and a vice-mayor. Writes Webb: “China’s new 'prefecture' is nearly twice as large as the combined land masses of Vietnam, South Korea, Japan and the Philippines.”

At stake is control of sea lanes, fishing rights and large mineral deposits, as well as the question of who will exercise strategic dominance in the region. China seems bent on wresting that strategic dominance from the United States so it can become the region’s dominant power. Gone would be America’s decades-long capacity to maintain stability—and hence prosperity—in the region.

Webb is not the first to issue such a warning, but his piece accentuates a central reality of this unfolding drama—namely, that the drama is unfolding much more rapidly than most people in the United States realize. Asia is watching to determine whether America will, as Webb puts it, “live up to its uncomfortable but necessary role as the true guarantor of stability in East Asia, or whether the region will again be dominated by belligerence and intimidation.”

China today represents the most fundamental geopolitical challenge facing the United States, and it has been a long time since the need for American boldness and imagination has been as acute as it is now in light of the Beijing challenge. Therefore, not only must next year’s president respond to this challenge, but he must also prepare the nation for it. That suggests a number of policy imperatives.

A smooth exit from Afghanistan: Upon taking office, President Obama ratcheted up the Afghan mission to include a major counterinsurgency effort, which meant a large dose of nation-building. Since then, he has ratcheted down the mission under a concept called “Afghan good enough.” What this means precisely has not been spelled out by the president, who has said, however, that by the end of 2014 Afghans will be “fully responsible for the security of their country.”

In light of the China challenge, “Afghan good enough” is not good enough. And a vague 2014 deadline, without any clear explanation of what kind of U.S. effort would continue beyond that time, lacks the kind of policy clarity the country needs. In his book on Obama’s foreign policy, Confront and Conceal, the New York Times’ David E. Sanger writes that a decade from now visitors to that country will see few traces of the American experiment there—“apart from military hardware and bases.” In reality, though, there is little need for U.S. bases in Afghanistan. Al Qaeda is washed up in the region (though problematical elsewhere); the Taliban doesn’t represent any kind of major threat to America; the Afghans will go their own way, as they have for centuries notwithstanding multiple efforts to subdue the place; and the United States can’t afford the effort in terms of blood, treasure or focus.

Get right with Russia: In his recent book, The Revenge of Geography, Robert D. Kaplan writes that China’s ability to project power into the Pacific is made possible by its dominance over its Central Asian land borders, “from Manchuria counterclockwise around to Tibet.” He explains: “Merely by going to sea in the manner that it is, China demonstrates its favorable position on the land in the heart of Asia.” But it is not in the interest of Russia to have China serene on its western borders, positioned to increase its influence in Central Asia and control the extraction of valuable natural resources there. Neither is it in the interest of the United States (or Russia) to see China emboldened in its territorial demands in the Pacific because it feels secure in its land position.

Thus, if China represents America’s greatest strategic threat, a strong relationship with Russia represents one of its greatest strategic imperatives. It’s time for the United States to downplay its discomfort with Russia’s authoritarian rule and widespread civic corruption. As troubling as Russia is, it hardly represents the kind of evil entity that Franklin Roosevelt and Winston Churchill snuggled up to during World War II. As a regional power, Russia has legitimate regional interests, and the United States should acknowledge those and incorporate them into its effort to establish a sound and mutually beneficial relationship with Russia—one that, if necessary, can be helpful in any future confrontation with China.

Avoid war with Iran: The United States currently is on a path to war with Iran, and it is a path that was blazed primarily by Israel, which has issued threats of a possible unilateral strike against Iran to stiffen America’s stance against the Islamic Republic. So far, Israeli Prime Minister Benjamin Netanyahu has managed to get Obama to foreclose any U.S. acceptance of an Iranian nuclear weapons capability (meaning no deterrence policy). That leaves open the question whether the United States should permit—and whether Iran would accept—low-level uranium enrichment for peaceful purposes only. Netanyahu is against such an approach, and it isn’t clear it could pave the way to a peaceful resolution of the issue in any event. But the current tough sanctions will not, in and of themselves, get the desired response from Iran if that response entails an Iranian humiliation. That’s why the peaceful-enrichment approach should guide U.S. thinking on the matter, even if that means an open rupture with Netanyahu. The American people would rally behind the president in such circumstances if the president levels with them about the stakes involved. U.S. leaders shouldn’t get sucked in to the kind of journalistic saber rattling that was visible on last week’s cover of The Weekly Standard, which showed a photo of Iran’s Supreme Leader, Ali Khamenei, under the headline: “The Most Dangerous Man in the World.” America’s most dangerous threat is thousands of miles from that man. And the United States should not seek a military confrontation with Iran, if it can be avoided, because such a conflict would pulverize the global economy and likely unleash far more instability into the region.

No more U.S. boots on the soil of Islam: The Middle East is in turmoil, and the entire region is in danger of being destabilized by the civil war in Syria. Events there could deal a heavy blow to the interests of the United States, the West and much of the rest of the industrialized world. Actual U.S. military action could prove necessary to stabilize the region, but the United States should do everything possible to avoid such a course. Another U.S. intervention in the region would prove highly incendiary. But sitting by and watching is not an appropriate policy either. The situation calls for deft, imaginative and stealthy efforts, always in conjunction with Islamic powers in the region, particularly Turkey, to avert the worst possible outcomes and keep the situation under wraps to the greatest extent possible. The pressures for U.S. involvement in Syria on humanitarian grounds should be resisted forcefully.

The need for economic growth: Obama has not been a successful president in the economic realm. Economic growth has been languid throughout most of his presidency. This needs to change abruptly. But addressing the growth problem without exacerbating the country’s ominous debt problem isn’t going to be easy. That’s why the next presidential term must be devoted assiduously to a comprehensive fiscal reform designed to address out-of-control federal spending while boosting economic activity and growth. Entitlement reform will have to be combined with a comprehensive tax reform that slashes tax rates while eliminating large numbers of tax preferences, including many that have been considered sacred cows for decades. Only by restoring its fiscal health can the country face major challenges of the kind that looms in Asia. But this will take presidential leadership in abundance, the kind of leadership that we have not seen for a long time.