From plans for a border wall with Mexico to praise for Vladimir Putin, Republican Donald Trump’s statements made the 2016 U.S. presidential race a campaign like no other.
Now, his upset victory in the November 8 election has left the world asking what can be expected from a Trump presidency -- and whether his policy proposals will be implemented.
Because of the system of checks and balances created by the U.S. Constitution, much depends on whether the U.S. Congress supports the policies Trump proposes.
Trump will need backing from the legislature or the judiciary if he is to implement campaign promises like cutting taxes on businesses, changing the country’s libel laws, or overturning President Barack Obama's health-care reforms.
But experts say that Trump could implement many of his plans simply by issuing executive orders.
In fact, a transition team that Trump has had in place for months has been identifying about 25 executive orders he could sign immediately after taking office on January 20.
In terms of foreign policy, "The president's powers theoretically are immense," said Dana Allin, a U.S. foreign policy expert at the London-based International Institute for Strategic Studies (IISS).
"It's very difficult to see how those would be easily constrained by Congress," Allin said. "The president is in a position to do a lot in this area -- to make decisions about the disposition of troops about whether to take military action. I'm not sure there would be much control over him."
Here are some of the positions Trump has staked out:
Russia And NATO
Trump has said he would rather "have Russia friendly" to the United States than "the way they are right now," contending that warmer ties would mean the two countries "can go and knock out" the Islamic State militant group together. He has also voiced confidence that he could easily reverse the drastic downturn in relations.
He said in September that he "would have a very, very good relationship" with Russian President Vladimir Putin and has also asserted that he would be better at negotiating with Putin than President Barack Obama has been.
Trump's critics question that confidence, noting that Obama sought to improve relations with Russia with his first-term "reset." They also question whether Trump would be willing and able to stand up to aggressive moves by Russia against the United States and its allies.
Trump has shown admiration for Putin, calling him a better leader than Obama. And in March, he called NATO "obsolete," saying he would withhold U.S. support from alliance members unless they increased military spending and "fulfilled their obligations" to the United States.
WATCH: NATO Chief Says Alliance Important To Europe, United States
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NATO Chief Says Alliance Important To Europe And United States
Henning Riecke, head of the U.S.-Transatlantic Relations program at the German Council on Foreign Relations, says that if the United States "leans more to the Russian side" during Trump's presidency, it could have "direct and very dangerous repercussions for European security."
Trump will face a "reality check" if he tries to renegotiate NATO burden-sharing, Riecke said.
"This is one of the most important bases of American superpower status -- that they promise to protect their allies," he said of the United States, adding that Russia would be likely to exploit any gaps in Western defenses and deterrence.
Moscow is likely to "do whatever it can to weaken" NATO and the European Union in order "to win more influence, especially in...Central Asia and Eastern Europe," Riecke said. "If a U.S. president would do that job for Russia, Putin would be happy about it."
Iran Nuclear Deal
Trump will have the authority to carry out his pledge to try to renegotiate the 2015 deal under which Iran is curbing its nuclear program in exchange for sanctions relief.
But Riecke said that would be "very difficult because it would mean to bring in some of the partners that also were at the table -- among them Russia and also the EU."
Such an attempt would "play into the hands of the hard-liners in Iran,” he said, probably scuttling the deal and making it harder to prevent Tehran from seeking nuclear weapons.
Nuclear Nonproliferation
Trump has declined to rule out the use of nuclear weapons against Islamic State militants and has suggested that South Korea and Japan should start work to develop their own nuclear weapons.
Riecke and Allin said Trump's campaign rhetoric could lead to the erosion of nuclear nonproliferation efforts globally. Countries "might really have to consider their security position and whether they need nuclear weapons," Allin said, speaking before November 8.
The Environment
Trump has said that "the concept of global warming was created by and for the Chinese in order to make U.S. manufacturing noncompetitive."
As president, he will have the authority to carry out his promise to pull out of the Paris Agreement that limits the greenhouse-gas emissions linked to global climate change.
Trump, whose energy and environmental policies are widely backed by Republican lawmakers, has also vowed to reduce federal environmental regulations.
Through executive orders, he could potentially reopen oil exploration in protected areas of Alaska and the Arctic Ocean, and allow work to begin again on an oil pipeline from Canada that was suspended by Obama.
Immigration
Trump has promised to round up and deport all of the 11.3 million undocumented immigrants in the United States within two years and has vowed to create a "deportation task force" to implement the plan.
The funding for such a program would require congressional approval, and some Republicans have opposed the idea, which is unpopular with Latino voters and fiscal conservatives.
Analysis by the American Action Forum, a conservative Washington think tank, says fully enforcing Trump's plan in two years would "require an unprecedented expansion in U.S. immigration enforcement personnel and infrastructure."
It also said removing all undocumented immigrants from the United States would lower the country's real gross domestic product by $1.6 trillion -- and that doing so in two years could result in a "sudden and deep recession."
There also are doubts about Trump's plan to build a wall along the southern border of the United States and make Mexico pay for it.
Mexico says it won't pay for the project, which The Washington Post has estimated would cost at least $25 billion.
Trump suggested he could confiscate remittances from undocumented Mexican immigrants under the U.S. Patriot Act, but legal experts have questioned whether a law designed to stop funding for terrorists could be used for the purpose.
Also on immigration, Trump could issue executive orders to implement his controversial proposal to temporarily ban Muslims from entering the country and to suspend refugee programs.
Both moves would probably be challenged in court, but it could take a long time for a court ruling to resolve complaints.
Tax Cuts
Trump has proposed a supply-side economic plan based on the idea that cutting business taxes to 15 percent from the current maximum of 35 percent would create jobs and economic growth by encouraging companies to invest.
Republicans generally support such tax cuts. But there is opposition from independent and bipartisan economic groups as well as some fiscal conservatives.
The Tax Foundation, a nonpartisan think tank in Washington, estimates that Trump's proposed tax cuts would "reduce federal revenue" by up to $5.9 trillion dollars -- without taking into account increased economic growth – and would mean significantly lower taxes for the wealthiest citizens.
In an October report for the Urban-Brookings Tax Policy Center, New York University Law School Professor Lily Batchelder concluded that Trump's plan would "significantly raise taxes for millions of low- and middle-income families with children."
The Committee for a Responsible Federal Budget, a bipartisan public policy think tank in Washington, estimates that Trump’s proposed tax cuts would raise the overall U.S. debt to $28.4 trillion by 2026.
Trade Agreements
Another part of Trump's economic plan is based on his view that U.S. businesses suffer from a series of trade agreements that have been "a disaster" and should be renegotiated.
As president, Trump will have the legal authority to withdraw from the Trans-Pacific Partnership (TPP) trade pact and the North American Free Trade Agreement (NAFTA). He also could order the U.S. Commerce Department to bring trade cases against countries like China, which he has threatened to do, and impose tariffs on specific categories of imports.
Trump also has threatened to pull the United States out of the 164-country World Trade Organization (WTO), which acts as an arbitrator in disputes over tariff agreements and trade rules, if it rules against his trade policies. He would have the legal authority to do so.
An assessment by Mark Zandi, the chief economist at Moody’s Analytics, says Trump's policy proposals would "significantly" weaken the U.S. economy by reducing cross-border trade, immigration, and foreign direct investment.