Concerned about the outcome of the U.S. presidential race, the world has been watching closely as Democrat Hillary Clinton and Republican Donald Trump tout their plans for handling terrorism and other global issues.
A former secretary of state who has advocated a more assertive U.S. policy in Syria, Clinton says she wants to use "all the tools of power" – from diplomacy to development – to support American foreign policy.
"I believe in strong alliances, clarity in dealing with our rivals and a rock-solid commitment to the values that have always made America great," Clinton said in a foreign policy speech in June. "And if America doesn’t lead, we leave a vacuum – and that will either cause chaos, or other countries will rush in to fill the void."
Jeremy Mayer, a professor of political science at George Mason University, calls Clinton an "internationalist" and "multilateralist" – an advocate of American global leadership in the mold of President Barack Obama.
"Where she’s different from Obama is, I think, she’s more willing to use force," Mayer says.
Though his opposition to "nation building" and other positions put him in the realist camp of foreign policy, Trump is seen as a unilateralist and even an isolationist – his pledge to put America first harkening back to another period of American isolationism.
"To our friends and allies, I say, America is going to be strong again, America is going to be reliable again," Trump said in a major foreign policy speech April. "We’re going to finally have a coherent foreign policy based upon America’s interests and the shared interests of America’s allies."
Invoking a phrase popularized by Ronald Reagan, Trump vowed to project "peace through strength" by restoring American military might, a theme that resonates with his ardent backers.
A Trump presidency "will strike fear in the hearts of those that have been taking advantage of us," says Sidney Shachnow, a retired Army general who joined 87 other former generals and admirals in endorsing Trump last month.
Of all the foreign policy differences between Clinton and Trump, few are as revealing as their discord over America’s commitment to NATO and other alliances.
Trump set off a firestorm this summer when he suggested he would not automatically come to the aid of NATO allies if they came under an attack by Russia.
The comment drew a sharp rebuke from across the political spectrum, but Trump has not softened his insistence that NATO members pay "their fair share" on defense and focus on combating terror.
The differences came into sharp relief during the second presidential debate earlier this month.
"We’ve got to work more closely with our allies, and that’s something that Donald has been very dismissive of," Clinton said.
Trump responded by saying that America has been "working with them for many years, and that’s why we have the greatest mess anyone has ever seen."
To critics, that hints at a failure to recognize the importance of an alliance that has served as a bulwark of American security for nearly 70 years.
"What [Trump] fails to understand is NATO is in our interests," says James Jeffrey, a former senior diplomat who has endorsed Clinton. "It undergirds our security. Without NATO, we would be back like we were in 1917 or 1940 without Britain."
Trump supporters say their candidate has no intention of abandoning NATO or America's other alliances.
Trump "will pressure the participants in the alliance to carry their fair share of the burden and ease the burden for the American budget," Shachnow says. "But overall, the alliances [that] have served us well will serve us well in the future."
With the Kremlin accused of meddling in the U.S. presidential elections, Russia will remain a major foreign policy challenge for the next president.
Trump has called Russian President Vladimir Putin a strong leader and said he wants to build a relationship with him if only to fight the Islamic State terrorist group.
Trump’s running mate, Mike Pence, took a harder line during the vice presidential debate, calling Putin "a small and bullying" leader and saying Russian provocations "need to be met by American strength."
But Trump has stuck to his guns even as he's advocated European diplomatic pressure on Moscow.
"I don’t know Putin," he said during the second presidential debate. "I think it will be great if we get along with Russia because we could fight ISIS together as an example."
National security experts from both political parties have pilloried Trump for taking a soft line toward a resurgent adversary that is threatening American interests in Europe and beyond.
"He dismisses any threat of Russia," Jeffrey says. "And this is totally factually wrong and extremely dangerous."
Pledging to be "firm but wise with our rivals," Clinton has said she wants to strengthen sanctions on Russia imposed over its annexation of Crimea and invasion of Ukraine, expand U.S. missile defense systems in Europe, and help European nations break their dependence on Russian energy
"I stood up to Russia," she said during the second debate. "I’ve taken on Putin and others, and I’d do that as president."
If Clinton wants to stand up to an aggressive Russia, Trump vows to take on a rising China whom he has accused of "an economic assault on" the United States and of stealing well-paying jobs.
Trump has called for punishing Beijing for unfair trade practices, designating China a currency manipulator, stepping up U.S. military presence in the South China Sea, getting China to rein in North Korea and countering Chinese cyberattacks.
"China respects strength," Trump said in April. "By letting them take advantage of us economically, they’ve lost respect" for the United States.
Trump went on to warn that the two world powers could either mutually "benefit or we can go both our separate ways."
Clinton is far from soft on China – last week, she made headlines by suggesting a missile defense "ring" around China – but she’s also warned against unilateral U.S. action in any trade dispute.
Mayer, of George Mason University, says managing America’s increasingly complex relationship with China will remain a challenge only surpassed by Russia for the next president.
"The Trump vision on China is for aggressive challenging militarily as well as economically, whereas the Clinton approach to China is again to be a military ‘stop what you’re doing’ policy. But she wants to work with China in a more multilateral and diplomatic way whenever possible," Mayer says.
The 2015 international deal with Iran to halt its nuclear program remains another point of contention between the two candidates.
Clinton has taken credit for laying the groundwork for the deal, saying it has made the world safer. However, Clinton, who as secretary of state built international support for sanctions on Iran, also said she wants to re-impose and strengthen them if Tehran fails to comply
"I'm proud that we put a lid on Iran’s nuclear program without firing a single shot," Clinton told the Democratic National Convention in July.
Like most Republicans, Trump is a vociferous critic of the deal and has vowed to revoke it as soon as he’s elected.
"When I look at the Iran deal and how bad a deal it is for us, it’s a one-sided transaction, where we’re giving back $150 billion to a terrorist state, really the No. 1 terrorist state," Trump said during the second debate. "We’ve made [it] a strong country from, really, a very weak country just three years ago."
The Republican Party platform calls the agreement "a personal agreement between the president and his negotiating partners and not binding on the next president."
On the foreign policy issue most Americans care about – the Islamic State in Iraq and Syria – the policy differences between Clinton and Trump appear hardly distinguishable at first glance.
Both want the U.S. to step up airstrikes against Islamic State targets in Iraq and Syria; both advocate a no-fly zone over parts of Syria to prevent the Syrian government from targeting civilians and rebels; and both say they’ll work with an international coalition of Western and Middle Eastern countries to fight ISIS.
But the similarities end there. Clinton does not favor sending more ground troops to Syria and Iraq and has advocated taking a hard line on the regime of President Bashar al-Assad.
Contradicting his running mate on countering Russian "provocations" in Syria, Trump suggested during the second debate that there was no need to confront the Syrian regime, Russia and Iran as they were all fighting ISIS.
Trump sees the Islamic State as part of a larger threat facing America, which he calls "radical Islamic terrorism." He faults Clinton and Obama for refusing to "name the enemy."
"And unless you name the enemy, you’ll never, ever solve the problem," Trump said in April.
He says he’ll establish a commission on radical Islam if he’s elected but he has offered few other details about his larger plan to defeat ISIS, leaving many critics wondering how he'd take on the group.