In less than two weeks, President Barack Obama and Republican nominee Mitt Romney will square off in the first of a series of presidential debates that will include foreign policy. But who should they be drawing their inspiration from? And whose examples should they be avoiding?

Global Public Square asked a group of historians and commentators for their take on the most successful and least successful U.S. presidents, from a foreign policy point of view. Here, we feature their picks of the best, and on Friday, we'll highlight those considered the least successful. (All views expressed here are, of course, the writers' own.) Agree or disagree? Share your thoughts in the comments.

FRANKLIN D. ROOSEVELT

Bruce Jentleson is professor of Public Policy and Political Science at Duke University and the author, among other works, of "American Foreign Policy: The Dynamics of Choice in the 21st Century."

His take: Both for his leadership turning one of our country’s moments of greatest vulnerability into the triumph of World War II, and for the vision to begin building the postwar peace, Franklin D. Roosevelt deserves the highest ranking. Congressional isolationists had blocked most of FDR’s efforts to start mobilizing the American industrial base and preparing the American people for the war. We would have had our work cut out for us even if the Japanese attack on Pearl Harbor hadn’t crippled the Navy. FDR’s fireside chats provided a mix of reassurance and call to action. From only 175,000 troops, enlistments and the draft brought the military to 8.5 million. Government and industry worked together. American families did their share buying war bonds and growing “victory gardens” – including my then-14 year-old Mom who still had her official thank you letter for her Scranton, Pennsylvania plot of lettuce and tomatoes when she died more than 60 years later. And even before the war was over, he began laying the groundwork for a postwar order: the Bretton Woods open international economic system, the United Nations, diplomacy with the Soviet Union to at least try and avoid what later became the Cold War.

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James Lee Ray is director of undergraduate studies at Vanderbilt University.

His take: Franklin Delano Roosevelt is hard choice to avoid as most successful foreign policy president. He faced the greatest, most serious challenges, and he dealt with them successfully.

He managed to make important contributions to the anti-fascist effort even when faced with overwhelming isolationist opposition before 1941. (Lend-Lease, for example.) Japan attacked in 1941, and then Hitler declared war almost immediately. That declaration made it possible for him to focus on Europe first. His planning for the attack across the English Channel took a very long time. Meanwhile, the Nazis and Communists were killing each other by the millions. The difficulties faced by the Allies even in 1944 when the cross-channel attack was launched suggest that an earlier attack might have been premature and unsuccessful.

Holding together the Allied coalition was difficult. Adopting the policy of “unconditional surrender” was probably a key to doing so. He did put too much faith, at Yalta, in his ability to deal with Stalin after the war. He didn’t count on being dead when the time came. But it is unlikely that any policies would have prevented the Soviet Union from taking over in Eastern Europe, or the Cold War.

Andrew Bacevich is a professor of international relations at Boston University and a retired career officer in the U.S. Army.

His take: The measure of merit: A successful statesman enhances the wealth, power, and influence of the state; the unsuccessful statesmen depletes those assets.

Based on those criteria, Franklin D. Roosevelt ranks as our most successful foreign policy president. Thanks to FDR’s skillful management of World War II, the United States by 1945 had become the richest and strongest country in the world. Americans were the sole beneficiaries of the cataclysm touched off by Hitler’s invasion of Poland in September 1939. By the time the smoke cleared, the ranks of Great Powers had been reduced to two and in every way that counted, the United States enjoyed vast advantages over its only conceivable rival, the Soviet Union.

James M. Lindsay is the senior vice president and director of studies at the Council on Foreign Relations.

His take: In the spirit of the bipartisanship that Americans long for in their foreign policy but typically don’t see, two presidents rate as most successful in foreign policy: Franklin D. Roosevelt and George H.W. Bush. With the destroyer-for-bases-deal, the Lend Lease Act, and other actions, FDR secured critical support for Britain during its darkest hours and against intense isolationist head winds at home. He then led the country to victory in World War II and oversaw the creation of the bedrock international institutions of the modern world: the United Nations, the International Monetary Fund, and the World Bank.

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GEORGE H.W. BUSH

Thomas Schwartz is professor of history at Vanderbilt University.

His take: Two very different presidents who come to mind almost immediately are Harry Truman and Richard Nixon. Truman’s presidency laid the basis for the successful policy of containing the Soviet Union and built such important foreign policy institutions as NATO, through which American policy was exercised throughout the Cold War. He presided over the reintegration of Germany and Japan into the American led system of alliances. Truman did fight an unpopular war in Korea and fire a popular general, but his decisions have largely been vindicated by history even though they made him extremely unpopular as he left office. The other president is Richard Nixon, who with the help of Henry Kissinger reversed America’s decades-long estrangement from China and dramatically improved relations with the Soviet Union, playing the two communist giants off against each other. Although Nixon’s policy of ending the war in Vietnam was controversial, it was ultimately approved by the American people, who gave him one of the largest landslides in American history. But the collapse of his presidency over Watergate keeps his presidency from being seen as a success.

But the president I would select as the most successful post-1945 president in foreign policy is George Herbert Walker Bush. Bush came into the presidency during the tumultuous year of 1989, which saw the collapse of communism in Eastern Europe, and most importantly, the reunification of Germany. Not only did he manage these changes with an intelligence and modesty that facilitated America’s goals, he also worked quietly behind the scenes with his Soviet counterpart Mikhail Gorbachev to minimize any violence and bloodshed. At the same time, Bush engineered an extraordinarily effective international coalition to oust Saddam Hussein from Kuwait. He was a president who both recognized the potential strength of the United States, but also the limits of its power.

James Lee Ray:

His take: George H. W. Bush is surely the most highly qualified foreign policy president in the history of the country. He had been a Congressman, head of the CIA, ambassador to the United Nations, envoy to China and vice president of the United States for eight years by the time he became president.

And that experience seemed to pay off. He did launch a gratuitous attack on Panama in 1989. But then he put together the greatest, most powerful coalition ever (compared to its enemy), to push Iraq (and its million man army) out of Kuwait in 1991. He avoided the temptation to go into Baghdad. (Had he not, the hardline Communist coup in the Soviet Union in August of 1991 would have succeeded.)

Bush faced a situation in Germany after the end of the Cold War whose potential for disaster is also still under-appreciated. The Soviet Union still had 300,000 troops in East Germany. It did not want to see Germany united, and it considered a united Germany as a member of NATO totally out of the question. But President Bush managed to pull that off anyway, without creating a very messy crisis in the middle of Europe, with a desperate Soviet Union in its death throes.

James M. Lindsay:

His take: George H. W. Bush did not enjoy the FDR’s electoral success. But during his one term he successfully handled some of the stiffest foreign policy challenges of the last half century. He helped manage the peaceful collapse of the Soviet Union and pushed for the reunification of Germany against the advice of close U.S. allies. He also liberated Kuwait and resisted calls to send the U.S. military onward to Baghdad. No, the elder Bush never figured out what the “new world order” would look like. But then again, neither have his three successors.

RONALD REAGAN

Danielle Pletka is Vice President of Foreign and Defense Policy Studies at the American Enterprise Institute.

Her take: Measuring the relative success of American presidents in foreign policy is an almost impossible task. Even narrowing the task to the 20th and 21st centuries demands almost ridiculous comparisons. What are the metrics? Lives lost? Lives saved? American interests served? But which ones? Many might argue that Franklin Roosevelt was one of our nation’s greatest foreign policy leaders, ushering in the era of American global leadership, ridding the world of a vile dictator. But World War II was also a tale of missed opportunity; of lives lost because the United States would not act. Can any war that ends with the death of six million Jews be considered a “success”?

Then too, there are contests, many partisan, for the title of worst foreign policy president. Was it Lyndon Johnson, who failed to successfully prosecute the Vietnam War and sacrificed tens of thousands of American lives only to see us leave a few short years later? Was it George W. Bush, scourge of liberals for beginning the Iraq War, a conflict supported by the United States Congress but long and complex in its undertaking? Or Jimmy Carter, for whom ideology was paramount, therefore allowing the Soviet invasion of Afghanistan and the Islamist takeover of Iran?

There are no serious answers to the question because American leadership doesn’t lend itself to a neat, nonpartisan dissection of our presidents. Different Americans want different things for our country, and even those Americans aren’t divided into neat partisan lines. There are Republicans and Democrats for retreat; conservatives and liberals for internationalism.

Still, two men vie for the title of best and worst, though each has many competitors. Each governed at a seminal moment, and saw the United States through a crossroads, determining a path that would govern our future for many years.

Ronald Reagan had a vision for America in the world. Importantly, his ambitions for America’s role on the world stage were not shaped by our enemies, but rather shaped by his own view of American exceptionalism. Reagan hastened the end of the defining battle of the 20th century, the fight between those who believed in freedom and those who embraced communism. True, there were bad choices of allies (Pinochet, Savimbi), but in the aftermath of the Carter era – dominated by a president who believed American power was an embarrassment to be lived down – Reagan knew not only what the United States opposed, but what America supported: freedom in all its iterations.

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Honorable mention

JIMMY CARTER

David Ryan is professor of history at University College Cork, Ireland and author of Frustrated Empire: US Foreign Policy from 9/11 to Iraq.

His take: Jimmy Carter reflected in his second State of the Union that it was “sound.” The troubles of 1979 had yet to compound his presidency. Carter reflected that on his watch, not one American service person had died abroad. He asked his audience, in words that now seem incredibly ironic, what sort of world the early 21st century would be as that generation of kids grew up – would America be at war? “Our children who will be born this year will come of age in the 21st Century. What kind of society, what kind of world are we building for them? Will we ourselves be at peace? Will our children enjoy a better quality of life? Will a strong and united America still be a force for freedom and prosperity around the world?” Little did he realize that it would witness two presidents trying desperately and ineffectively to withdraw from two theaters of combat with mixed results.

Of course, Carter was weak! Or so the conventional narrative ran. He received constant advice that he had to hit someone, somewhere. Americans were confused about the direction of his foreign policy. Americans had been taken hostage, the Soviets had moved into Afghanistan, the Sandinistas had succeeded in Nicaragua and Carter moved around the White House in indecision: such is the caricature.

Yet Carter realized that the use of force in each of these instances would be counterproductive. On Iran especially, he confessed to an interviewer that bombing Tehran might make the country feel good, perhaps if timed well, he might have even been re-elected. But in terms of local and specific objectives, he would not have advanced the agenda much. Despite his early rhetoric, his was a more cautious and realistic presidency. After a decade and more of the atrocious use of force, he recognized the limits of U.S. military power and the power of the country’s appeal. That it did not work is in part due to the domestic discourse that straitjacket presidents in so many ways, limiting their choices, generating expectation, frequently of a pugnacious sort, and most insidiously questioning their “credibility” should they fall short.

THOMAS JEFFERSON

Bruce Jentleson:

His take: Thomas Jefferson gets my second nomination, principally for his deft diplomacy in pulling off the Louisiana Purchase. These 820,000 square miles, encompassing an area that eventually would include all or part of 14 new states and provide the gateway opening the Far West, transformed our small Atlantic Coast country into a vast continental one. Despite blustery urgings from Alexander Hamilton to try to seize these areas militarily, Jefferson got it done through skilled statecraft. He played French-British-Spanish rivalries off one against the other. And when he and his emissary James Monroe saw how much Napoleon needed the money, they savvily shifted from their original plan to buy just the port of New Orleans for $10 million to dealing for all that territory for just $15 million.

None of the above:

Scott Lucas is a professor of American and Canadian Studies at the University of Birmingham, England.

His take: I don’t think there is a best, at least in the post-1945 world, because each of them has been limited by the demands of American power. Franklin D. Roosevelt might have prevailed with a vision of the “international” had he not died in office, but Truman and Eisenhower were both caught up in the confrontation with the Soviet Union – the good of the Marshall Plan has to be set alongside not-so-good U.S. interventions outside Western Europe. Kennedy’s inaugural address is one of the most aggressive speeches ever delivered and partly-implemented, Johnson sank in Vietnam, and Nixon complemented “détente” with a cynical U.S. policy that rampaged through much of the world from Cambodia to East Timor to Chile. Reagan? Overrated – the fortuitous economic exhaustion of the Soviet Union saved him from a less-exalted reputation built on the excesses of U.S. power, such as Iran-Contra and the aftermath of 1980s Afghanistan.

Jimmy Carter could have made a difference, but his well-intentioned attempt to shift U.S. policy to international justice and rights was sabotaged by the Soviets, Congress, and an inability to deal with cases like Iran.

But the one lost chance of “best” that sticks with me is seeing the last overseas speech of Bill Clinton, given in December 2000 in Warwick, England. He spoke in a tired but eloquent voice of the necessity to meet the challenges of climate change and global warming, epidemics and basic health care, and the vast divide in living standards. And I thought, “Great speech. What have you been doing for the last eight years?”

What do you think? Which president set the bar when it comes to U.S. foreign policy? Who would you argue in favor of? Against? Share your thoughts in the comments below.