After a bruising brawl of a campaign, the next US commander in chief will inherit a world with the toughest array of foreign policy challenges in decades.

The President's Situation Room meetings will focus on hot, cold and simmering conflicts around the globe, all playing out as Russia and China seek greater international clout, cyberattacks become increasingly disruptive, and long-time US allies worry about Washington's support.

Middle Eastern conflicts in Syria and Iraq are re-igniting sectarian tensions and sending destabilizing waves of refugees across the region and into Europe, where their presence is altering political dynamics.

Asia is on hair-trigger alert because of an unpredictable North Korean leader who is improving his nuclear arsenal at an alarming rate. China is challenging US power in the South China Sea, while Russia is placing nuclear-capable missiles on NATO's doorstep and opposing the US in Syria. Some national security problems are so big, no one country can deal with them -- climate change and the as-yet-unwritten norms of cyberwar among them.

The next president will confront "black swans" -- disruptive events that no one sees coming -- but they will also face some certainties, chief among them that foes will test their resolve not long after they move into the Oval Office.

An 'early challenge' likely

"I expect an early challenge," said Mark Dubowitz, executive director of the Foundation for the Defense of Democracies.

Dubowitz expects "a forceful challenge" on Iran and said the new "administration will have to be prepared to have a full menu of responses, proportionate and disproportionate."

Other analysts predict early tests from Europe and Asia, too. In Russia, President Vladimir Putin bears no warmth for Hillary Clinton, a former secretary of state whom he believes instigated protests against him in 2012. And North Korea has a demonstrated track record of provocative acts -- missile launches or nuclear tests -- within a month-long window before or after a US presidential election.

"The North Koreans are certainly going to challenge the next administration," said Victor Cha, a senior advisor at the Center for Strategic and International Studies who was President George W. Bush's top adviser on North Korea.

The isolated Asian nation poses one of the toughest challenges for the next administration, Cha and others say. Pyongyang's erratic leader Kim Jong Un marked his aggressive pursuit of nuclear weapons with a fifth nuclear test in September and seeks the missile capability to deliver warheads to the continental US.

The Obama administration's policy of strategic patience, involving sanctions, international isolation and tough talk, has done nothing to dissuade them. "The notion of giving up their nuclear capability, whatever it is, is a non-starter," Director of National Intelligence James Clapper acknowledged in October.

"The problem is much worse than it was eight years ago," Cha said, and it will require the next administration to take decisive steps, such as sanctioning Chinese companies that do business with North Korea or changing its policy on missile defense.

A Cold War coming with China?

A tougher stance on North Korea will likely roil China, Pyongyang's protector and ally, so that "it would become much more like a Cold War with China in the region," Cha said.

China is already set to be a challenge for the next president. Increasingly, Beijing is using its military to assert claims to contested areas of the South China Sea that the US insists should remain open to international navigation and be peacefully resolved.

Clapper, speaking at the Council on Foreign Relations, noted China's "extensive military modernization program" across many fronts, including space, a development he described as "both disturbing and also impressive."

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A former top administration official said the next president will have to deal with a China that "feels like it's their time" and is intent on challenging US leadership of the global order, along with institutions like the G20. The next president's challenge will be to find areas of common ground while dealing with Beijing's assertiveness.

The next president will also have to reinvigorate relations with Asia, where core allies like South Korea are going through political upheaval, and in places do some repair work, as in the case of the Philippines, whose fiery President Rodrigo Duterte seems to be orienting his country away from Washington and toward Beijing.

China's muscle-flexing is part of a larger shift to a "multipolar construct where countries like Russia, like China, see themselves as important if not dominant players in this world scene," Clapper said.

US-Russia tensions grow

Tensions between Washington and Moscow have intensified as Putin has pushed back hard against US power globally over the last eight years, annexing Crimea, sustaining a low-level conflict in eastern Ukraine, threatening NATO allies in the Baltics and backing Syria's President Bashar al-Assad, whom the US opposes.

Putin has walked away from arms control and non-proliferation treaties with the US, threatened the tactical use of nuclear weapons and put new ICBMs and nuclear capable missiles in Kaliningrad, right beside Washington's NATO allies Poland and Lithuania. Russia has also conducted unprecedented cyberattacks against Democrats during the election.

"A year ago, I would have said the relationship is the worst since" the end of the Cold War, said Angela Stent, director of the Center for Eurasian, Russian and Eastern European Studies at Georgetown University. "But it's gotten even worse."

As tensions have risen, channels of communication have broken down, a dangerous situation, said Matt Rojanksy, director of the Kennan Institute at the Wilson Center. Among the risks the next president faces is the prospect that frozen conflicts that Russia uses to wield influence in places like Georgia, Ukraine and Moldova "could become shooting wars," Rojanksy said.

Russia has also been wooing traditional US allies in the Middle East, courting Egypt and Turkey at a time when Washington's relationships in the region have been badly strained. Those tensions within the Middle East are, in large part, byproducts of five years of upheaval that started with 2011 uprisings that have upended countries across the region.

Some Arab states -- Syria, Iraq, Libya and Yemen -- have fragmented, while others like Egypt are dysfunctional. Transnational terror groups such as ISIS, Ansar al-Sham and al Qaeda are feeding on the power vacuums. Meanwhile, Iran continues its support for terrorist groups across the region.

Inheriting a messy Mideast

In short, the next president will inherit a Middle East that Clapper calls "a mess."

"It makes your head hurt, it really does," he added. Moreover, in the last eight years, US relationships in the region have changed profoundly and will require rebuilding."

Authoritarian leaders, both friendly and adversarial, with whom the US has worked have either been purged or become enemies. Personal animosity between President Barack Obama and Israeli Prime Minister Benjamin Netanyahu have strained US-Israel ties.

Traditional allies in the Gulf were angered by Obama's reluctance to arm moderate rebels in Syria and his decision not to enforce a "red line" he'd drawn about the regime's use of chemical weapons.

Ties with Turkey fraying

Relations with NATO ally Turkey have frayed, too. Most recently, the government has accused a US resident of planning a July coup attempt and wants Washington to extradite him. So far, the US has declined to do so, adding to the frustration Turkey already feels about the US-backed campaign to oust ISIS from neighboring Iraq.

Turkey remains vehemently opposed to US cooperation with Kurdish groups in Syria that Ankara says are linked to terrorists but Washington sees as the most effective fighting force on the ground.

"At this point, the US lacks its traditional friends and our traditional adversaries are gone as well," said Aaron David Miller, a vice president at the Wilson Center.

The Kurdish question will be one of many facing the next president when it comes to Syria, where a civil war of more than five years has killed close to a half-million and created one of the worst humanitarian crisis of modern time.

More than 11 million people have been forced to flee their homes, with more than 4 million straining neighboring countries like Jordan, Turkey and Lebanon and fueling a migrant crisis in Europe. The chaos has fueled ISIS' rise and paved the way for Russian military intervention in support of the regime.

Josh Landis, who heads the Center for Middle East Studies at the University of Oklahoma, said Syria will be a difficult test for the incoming president.

"We have to make some hard choices about who we are going to support in Syria," he said. "If we support the Kurds, we alienate the Turks. If we support the Turks and rebels, we have to escalate with Russia and pull the rug out underneath the Kurds."

The next president will also have to confront the threat of ISIS and other extremist groups that have made Syria their incubator. They will require the US "to be in the business of suppressing these extremist movements for a long time to come," Clapper said.

The history of ISIS "is one of resilience and flexibility," he said. When the terror group is eventually expelled from its current strongholds in Iraq and Syria, it will probably "morph into something else or other similar extremist groups will be spawned," he said.

That transnational threat and others will require the 45th US president to work in close cooperation with other nations. One of the most pressing issues will be the thicket of questions surrounding aggressive acts in cyberspace by state and non-state actors. Those challenges are so new that the next president will have to work, in part with other countries, to define terms, said a former Obama administration official who worked on cyber issues.

"The questions will be, is it cyberwar, cybercrime or cyberespionage and how do you respond? What's a proportional response?" the official said. "This complex of issues will be on the front burner for the national security guys. Those are all novel questions."