If Mitt Romney wins the Republican nomination and is elected president next November, you can say goodbye to Barack Obama’s stated foreign affairs preference for “leading from behind.”

Romney’s foreign policy speech today at the South Carolina’s Citadel– his first lengthy foray into this political and policy mine field – rejected many of President Barack Obama’s key tenets.

Among them is the conciliatory and consensus tone of so many Obama foreign policy pronouncements. Romney, by contrast, trumpeted not just “strength,” but American economic, military, and political preeminence in international affairs. In sum, he said, as president, he would work to ensure that the current century was “an American Century.”

“In an American Century,” he said, “America has the strongest economy and the strongest military in the world.” It must “lead the free world” because if it doesn’t, “someone else will.” And that, Romney declared, would make the world “a far more dangerous place.”

He specifically rejected Obama’s rhetorical humble pie, the notion that the United States was just one of several equally balanced global powers. America was not just “exceptional“ in the way that “the British think Great Britain is exceptional or the Greeks think Greece is exceptional,” he said, a backhanded slap at a famous Obama speech. Such a view was “profoundly mistaken,” Romney declared. America was exceptional in that it had “a unique destiny and role in the world.”

In his Citadel speech, Romney seemed to be channeling Ronald Reagan. It was morning in America, in spades. America’s destiny to lead the world, he asserted, was a good thing, for America and for the world.

Here were a few of the differences he cited between himself and Obama:

1) He would “never, ever apologize for America,” as Obama has done.

2) He would not undermine American military strength as he claims Obama has done by cutting military spending.

He would, therefore, reverse the “hollowing of our Navy” and increase our shipbuilding rate – and presumably the nation’s job creation rate as well, from 9 per year to 15.

Unlike the current president, he would reverse Obama’s cuts to national missile defense and give priority to the “full deployment of a multi-layered national ballistic missile defense system.”

3) Unlike President Obama, he would not pursue efforts to deter Iran from developing nuclear weapons by trying to engage Teheran, but would “enhance our deterrent against the Iranian regime” by “ordering the regular presence of aircraft carrier task forces” in the Eastern Mediterranean and the Persian Gulf.

To signal to Iran that America intends to block its effort to acquire nuclear weapons at all costs, he would “begin discussions with Israel to increase the level of our military assistance and coordination.”

4) Unlike Obama, he implied, he would not let American force levels and the duration of our engagement in Afghanistan be determined by “politics,” but by “the best recommendation of our military commanders.” It is said that Gen. David Petraeus (ret.) and other senior American military commanders would have preferred to deploy a larger surge of forces for a far more open-ended length of time.

5) And unlike Obama, he would let American friends such as Israel and the U.K. know that America would stand by them “in an hour of need.”

“I will reaffirm as a vital national interest Israel’s existence as a Jewish state,” he said, a slap at the tense relations between Israel and the U.S. in response to Obama’s Mideast peace pressure.

“I will count as dear our Special Relationship with the United Kingdom. And I will begin talks with Mexico, to strengthen our cooperation on our shared problems of drugs and security,” he said.

In sum, Romney said, as president, unlike the current occupant of the White House, he would “not surrender America’s role in the world.” “This is very simple,” he said. “If you do not want America to be the strongest nation on Earth, I am not your president.”

Stirring words, indeed.

The problem, however, is that Romney’s speech is often more often at odds with President Obama’s rhetoric than his deeds.

For in national security and foreign policy, Obama has often been tougher than his sugary words imply.

For instance, while rejecting talk of a global war on terrorism – Romney says flatly that America is at war with “Islamic fundamentalism” – Obama has more than doubled the number of Predator and drone attacks against Al Qaeda, Taliban and Islamic militant targets in Afghanistan and northern Pakistan.

While vowing to close Guantanamo on “day one” of his administration, he has kept it open, and now asserts the right to indefinitely imprison prisoners of the war on terror there who are too dangerous to release and cannot be tried in military or civilian court.

While pledging openness and transparency, he has sharply boosted the number of Justice Department investigations and prosecutions of official leakers of government secrets.

He has killed Usama bin Laden and authorized the killing without judicial review of Yemeni cleric Anwar al-Awlaki, an American citizen.

While letting his aides speak of the benefits of leading from behind, he has helped topple Libyan leader Muammar Qaddafi and is ratcheting up pressure on Syria, whose president, Bashar al Assad, whom he says, has lost his legitimacy and right to rule by killing almost 3,000 of his citizens who have been peacefully seeking reform.

As for Iran, both Romney and Obama say that an Iranian nuclear bomb is “unacceptable.” But what that means in practice remains unclear -- for both of them.

So, too, the does the challenge of balancing America’s traditional support for pro-American autocrats of the Middle East with Washington’s endorsement of young Arabs’ demands for democratic reform and responsive and accountable government. Obama is alternatively pragmatic and idealistic in his stance, and I suspect a president Romney would be too.

Both Obama and Romney believe that restoring American economic strength is key to its ability to project power and influence abroad. But that goal, too, may continue to elude either of them.

Romney has struck an important theme of what would be his presidency: He has flatly rejected the isolationism advocated by so many politicians. America, he said, could not “crawl into an isolationist shell” or “wave the white flag of surrender.”

But in this belief he finds far more common ground with Barack Obama than with several of those seeking the presidency in his own party.

Judith Miller is a Pulitzer prize winning author and writer, and Fox News contributor.