The world expected President Obama to bring peace. Instead, he made war. When this Nobel Peace Prize recipient leaves the Oval Office, he will have the dubious distinction of having served as the longest wartime president in the history of the United States.

Is it possible that the reverse would happen with Donald Trump if he gets elected? Would he bring peace when the world expects him to make war?

Some anti-war activists on both the right and the left hope so. They are kidding themselves.

Make no mistake: Trump's bellicosity, hair-trigger temperament, disturbing tendency to see the world as "us versus them," and, above all, his militant protectionism will mean more war, not less.

Cato Institute's Doug Bandow has praised Trump's willingness to question the Washington elite that wants America to play global cop. Bandow has applauded Trump for his independence from the "neoconservatives and militaristic interventionists who dominate the Republican Party." Meanwhile, on the left, The Nation's Stephen Cohen declared that Trump was asking "fundamental and urgent" foreign policy questions that deserve to be engaged with.

There is no doubt that America's foreign policy establishment is stuck in a Cold War mindset. The Soviet empire has collapsed, the Berlin Wall has crumbled, and the Communist threat is long gone. But the NATO alliance that was forged after Word War II to keep Germany down, Russia out, and America in Europe has not just endured, but expanded. Likewise, America's involvement in the security of Japan, South Korea, and other Asian as well as Middle Eastern countries continues unabated. If these alliances cost Americans only money, they would be bad enough. But their existence has arguably destabilized regions, encouraging America to get embroiled in overseas conflicts that are none of its business, most notably the disastrous Libya intervention on President Obama's watch.

Trump's comments that these dusty alliances are "obsolete" and deserve to be overhauled would be welcome if they didn't stem from a radical xenophobia that sees any engagement with the world as a loser's game. Trump does not have a consistent philosophy against war. He opposed the Iraq war, albeit after the fact, but his criticism of Obama's Libya adventure was that it didn't happen soon enough.

Most troubling, however, is his prescription to "Make America Great Again" — which is to seal it off from the world by erecting walls, tearing up trade agreements, and forcing American companies to stay put. Trump may think that he's invented a brilliant new economic approach. In fact, it is so old — and such a perennial temptation for socialist dictators — that there is an actual term for it in economic literature: import substitution. Even in quasi-democracies like India, it has led straight to the poorhouse.

But that's not the main problem with it. As FDR's Secretary of State Cordell Hull noted, "If soldiers are not to cross international borders, goods must do so." (Some people believe that 19th century French political economist Frederic Bastiat made this statement.)

Indeed, it is practically impossible today to imagine England invading France or France invading Germany or Germany invading Poland. Their economies are too interdependent. As Nathan Collins has pointed out, before World War II (which, not coincidentally, broke out after America passed the Smoot Hawley trade act that raised average tariffs on foreign imports by 54 percent), military conflict was practically de rigueur in Europe. NATO's security guarantee didn't put an end to the great wars of dictators. Trade did. Indeed, the more countries trade and the more partners they trade with, the less likely they are to go to war. In 1870, countries on average had three trading partners. Now they have anywhere from 17 to 34. Conversely, the countries that one can most easily imagine coming to blows today don't trade. Think Pakistan and India. Or Pakistan and Afghanistan. Or North Korea and South Korea.

Trade doesn't eliminate all causes of war, but it does remove a major one: conquest to secure goods. So long as people can buy things from each other, they have less need to maintain armies to forcibly extract them. It is for this reason that Austrian economist Ludwig von Mises called the "philosophy of protectionism the philosophy of war."

In fact, trade doesn't just eliminate reasons for war, it generates forces of peace: Attacking your trade partner means either destroying your buyers or your supplier or both. Trade gives each side a stake in the other's well being.

All of this is lost on Trump. He views other countries not as possible partners in mutually beneficial exchange, but adversaries who are out to rip off America. Indeed, to the extent he wants to engage in any commerce with the world, it is from a position of strength — which is why making "our military so strong that no one will mess with America" is so important to him. Keeping alive the background threat of war when, say, accusing China of currency manipulation is a useful thing. Trump wants to buy and sell to other countries so long as he can dictate the terms. There are no carrots in Trump Land, only sticks. This is the Tony Soprano version of trade policy — especially in the hands of someone who regards any disagreement as a threat to his masculinity against which he will "punch back ten times harder."

Trump's foreign policy isolationism won't lead to peace because his trade policy isolationism will create the pre-conditions for war. George Washington understood this when he warned America to "steer clear of permanent alliances" with other countries in his Farewell Address, while at the same time counseling her to extend "our commercial relations."

Picking and choosing Trump's specific statements for praise just because they attack the "right" (pun intended) intellectual enemy won't correct America's conduct abroad as critics of neo-conservatism want. It'll put it on a more dangerous path. Sometimes our enemy's enemy is still our enemy.