As the United States contemplates military action against Syria, it must realize that it can no longer enter into and conduct wars in the way it has done since Korea. Vietnam was not really properly authorized or explained.

It was also mismanaged, in that — as General Eisenhower and General MacArthur both warned President Kennedy and President Johnson — it shouldn’t be attempted, but if it were, the supply flow from the North (the Ho Chi Minh Trail) had to be cut. It wasn’t. And MacArthur’s assertion that draftees cannot be asked to risk and give their lives in a cause less than a defined goal clearly in the national interest was demonstrated to be true, both morally and practically.

In Vietnam, the goal was never made clear; nor was the U.S. national interest clear, other than to avoid defeat once the country was engaged. That did not prevent the Democrats who plunged into the war from assuring defeat after President Nixon had disengaged the U.S. and preserved a non-Communist government in Saigon.

There should not have been two invasions of Iraq, though both were justified, militarily successful, and constitutionally impeccable; they were just politically mismanaged afterwards. With Bosnia, President Clinton invented the notion of a war worth killing for but not worth dying for; NATO aircraft flew at 30,000 feet to ensure risk-free bombing to the allies. (This was about the time that Mrs. Clinton fantasized that while little girls were curtsying and giving her flowers at Sarajevo Airport, she was actually under threat of her life from crackling sniper fire.)

George W. Bush had every justification to invade Afghanistan and led a great coalition in doing so, but then, leaving his allies undermanned and with an impossible mission, with, to say the least, insufficient thought and explanation, he decamped to Iraq with a much smaller coalition and leaped head-first into the bottomless morass of nation-building in both countries.

President Obama staved off what was shaping up as a complete disaster in Afghanistan, but now the U.S. is reduced to pleading with Pakistan to be less supportive of the anti-Western forces in Afghanistan and pursuing those elements for the privilege of discussing peace with them as we follow a pre-published and tight timetable for withdrawal from the country. It would be better just to leave without the window-dressing of fruitless negotiations where any agreements that are made will be ignored anyway. We went around that track in Vietnam, and in Iraq after the Gulf War.

With the latest twist in Syria, every previous criterion of national-security-policy formulation has been debunked. The entire process, built up over 75 years of generally successful policy planning under twelve previous presidents, six of each party, that led the West to victory in World War II and the Cold War, has just been jettisoned with the narcissistic breeziness this administration has brought to almost everything except disposing of bin Laden.

Even I could scarcely believe I was not watching “Saturday Night Live” or “The Gong Show” as the president, with Vice President Biden beside him — trying by his studiously grim countenance to contain the self-inflating hot-air balloon he seems to have as a brain — announced that he was sending his plan of a punitive but not really damaging cruise-missile strike on the Assad faction in Syria to the Congress, before having an afternoon of golf.

The national interest has to be defined. It has not been, in this case. What should have been done many years ago was that governments that committed outrages — especially terrorist outrages — against the West should have been marked down for overthrow when that could be done at moderate cost by assisting local dissidents. There should never have been the shilly-shallying in Libya that there was, that became an effective policy only thanks to the French. (And even the redemption of Libya was largely squandered by the administration’s shameful complicity in the murder of the U.S. ambassador in Benghazi, compounded by the macabre canard of Secretary Clinton’s Islamophilic television address to the Muslim world.)

The Assads have long been in this category, and in the early period of the uprisings, before 100,000 people were killed and 10 percent of the population fled in pitiful conditions, the U.S. and its allies, when it still had some, should have lifted the small finger necessary to dispose of Assad.

President Obama said Assad should go, just as he had said this about Qaddafi in Libya, but he did nothing to make this happen. He was the feckless Narcissus pulling the petals off the daisy: Assad should go, Assad can stay . . . As Bret Stephens aptly wrote in the Wall Street Journal on August 19, over the parallel debacle in Egypt, this administration seems unable to distinguish between a policy and an attitude.

It is no concern of the West whether the replacement government is better or worse for the Libyans and Syrians; that is their concern. We should never touch unsupported busybody nation-building again. Iraq and Afghanistan weren’t post-war Germany and Japan (sophisticated countries temporarily laid low) or even South Korea (a war-ravaged country eager to bootstrap itself up economically, with political institutions to follow).

What we have a right and duty to do is to dis-incentivize foreign countries from extreme provocations of the West. Just as Hamas stopped suicide attacks on buses and cafés in Jerusalem and Tel Aviv when Israeli premier Ariel Sharon killed the Hamas leader after each such outrage, there would be no more suicide attacks on the West if the ultimate instigators and facilitators paid with their lives, or at least their jobs, each time, despite their alleged yearning for the hereafter, as the cowardly, almost cave-dwelling, after-life of bin Laden illustrated.

International conventions should be attempted to define failed states and genocidal acts and to provide for international intervention to prevent failed states from becoming terrorist hotbeds, and to stop atrocities like the Cambodian Killing Fields and the massacres of Rwanda and Darfur.

Alliances are useful. The U.S. had allies when it led, and was perceived to be a reliable ally. NATO was the most successful alliance in history because it was an exclusively defensive alliance based on flexible response, and on the principle that an attack upon one was an attack upon all. The only time that clause was invoked was after the terrorist attacks of September 11, 2001.

Every one of the then 18 other member countries declared itself to have been attacked when the U.S. was — and George W. Bush and Donald Rumsfeld squandered that support. The closest allies of the U.S. historically, Canada and the United Kingdom, are not as predisposed to cooperate as they once were. The George W. Bush administration at least showed the gratitude of an ally to the British; the Obama administration has very unwisely shown not the slightest interest in maintaining any of these relationships.

The reset on Russia has been a complete failure, and the downgrading of European missile defense to ensure that Russia retained its first-strike capability on America’s Western European allies was a very serious mistake. George W. Bush’s aerated promotion of democracy assisted the Hamas and Hezbollah terrorist organizations and undermined the Mubarak government in Egypt, which is already regarded with general nostalgia.

Jimmy Carter wrote the playbook on what not to do with his shameful meddling in Iran and the world; the Iranians in particular are still paying for it. No interested American should fail to understand the significance of the British Parliament’s rejection of Prime Minister David Cameron’s request for authority to join the U.S. in action in Syria. The British often change leaders who have not handled military action well:

They did so in the Seven Years’, American Revolutionary, Napoleonic, Crimean, and both World Wars, and after the Suez expedition in 1956, but that country has never denied authority to take military action to a prime minister who asked for it. Cameron is probably finished, but so, for now, is the British alliance with the U.S. The Grand Alliance of Roosevelt and Churchill and the Special Relationship of a sequence of leaders of both countries, especially Reagan and Thatcher, has come to this: political, moral, and strategic bankruptcy. And this president is chiefly responsible for it.

President Obama and his claque have unlearned the fact that you can’t declare red lines and then back away from them. It has happened in Iran, and now in Syria, and only creates a vacuum that will be filled by the most odious elements around.

More serious than all of this is the abdication: Each president swears to execute the office faithfully and to preserve, protect, and defend the Constitution. Shuffling the role of commander-in-chief onto the Congress (in which no one, American or foreign, has the least confidence, and with good reason) is both cowardly and offensive to the Constitution, and aggravates the War Powers Act (which is itself unconstitutional and should be challenged).

Harry Truman famously said that the buck stops with the president. If Mr. Obama is not prepared to do the job he should not have run for it. The next three years will be an agony; it can only get worse, challenge to the imagination though that is.

cbletters@gmail.com. From the National Review.