As demand starts to build on President Barack Obama to “do something” about the deteriorating situation in Syria, let’s review where the U.S. and its citizens stand on the general question of using military force abroad.

On this issue, Americans are divided in strange ways. It’s no longer a matter of hawks and doves. There are liberal hawks and conservative doves as well as conservative hawks and liberal doves.

Liberal doves oppose almost any use of U.S. power because their mindset hardened during Vietnam. War kills children and other living things. We can’t be the world’s policeman, and so on. This sounds dismissive, but it’s not meant to be. In fact, it’s more or less where I come out.

Then there are liberal “bleeding hawks,” who see a humanitarian catastrophe developing in Syria — or virtually any place else in the world where there is strife of any kind — and think that the world’s only superpower (for the moment) must not stand idly by. This is what we did for too long in the Balkans, while thousands died.

Conservative doves have roots that go back further than Vietnam, to the pre-World War II isolationism — and sometimes overt fascist sympathies — of groups like America First and people like Father Coughlin. This group is nourished by pathological hatred of Democratic presidents from FDR through Obama, and its members tend to reflexively oppose anything these presidents propose or do on any topic, foreign or domestic.

America the Powerful

Conservative hawks, by contrast, reflexively favor almost any use of American power because, well, it’s American and powerful. That sounds dismissive, and it’s meant to.

This group includes the so-called neocons, and because most of the action since the end of the Cold War has been in the Middle East, they are sometimes suspected of carrying water for Israel. That’s unfair. An odd combination of macho and scaredy- cat, they see peril to the U.S. everywhere, and want to stamp it out.

This taxonomy leaves out the foreign policy “realists,” mainly but not always Republicans (of the no longer extant “Rockefeller” or “liberal” variety), and mainly but not always anti-intervention. Self-described “realists” pride themselves on their steely focus on national interests and power politics — no idealism, here, please. Their high priest is George F. Kennan, who came up with the Cold War policy of “containment.”

Another group in this debate that crosses party and ideological lines might be called the new constitutionalists. These people have noticed that the Constitution requires a president to get the approval of Congress before going to war.

This provision was largely ignored during the Cold War. It was considered impractical when possible conflicts were likely to be low-grade guerrilla wars, or top-secret CIA mischief, or quick nuclear exchanges that would be over, with millions dead, in 45 minutes. None of these styles of combat lent themselves to a leisurely debate out of the 18th century.

Today’s wars, however, are perfectly suited to what the Constitution requires: They are deliberate, highly optional decisions made by the U.S. to initiate hostilities, after months of television yak that is no substitute for a relatively dignified senatorial debate. (The Constitution requires the debate, not the yak.)

The situation in Syria is further complicated by the familiar question of who’s the good guy. The bad guy is clearly Bashar Al-Assad, another son of a dictator who has gone into the family business. But his opposition is a mixture of unattractive clerics and their followers, liberal reformers, and left-wing radicals. Traditionally we have anointed a pro-U.S. figure as our boy, such as Ngo Dinh Diem in Vietnam, Arturo Cruz in Nicaragua, Ahmed Chalabi in Iraq, or the current favorite, Hamid Karzai in Afghanistan, and traditionally he disappoints us.

Maximum Force

Our guiding star in questions of intervention used to be the (Colin) Powell Doctrine, named for the admired retired general. The Powell Doctrine held that the lesson of Vietnam is: If you are going to intervene in some distant land, do so with maximum force for a quick victory and the uncomplicated support of the citizenry back home. This standard can almost never be met (which may have been Powell’s point). It was, in effect, a recipe for isolationism.

So the Powell Doctrine has been ignored: successfully in places like Kosovo, and somewhat less successfully in Afghanistan and Iraq. In both these latter cases, we forgot another supposed lesson of Vietnam, which is that to avoid a “quagmire,” you need an “exit strategy” — some way to get out short of total victory, in case that latter option is not available. But your exit strategy cannot be a “hard and fast deadline,” as Obama has promised in Afghanistan and achieved in Iraq, because that tells the bad guy that all he has to do is hang on until Date X and he wins.

People used to make a great distinction between America’s interests, America’s values and purely humanitarian concerns. Intervention to protect the first was regarded as mandatory, serving the second and third was not.

In practice, at least in the Middle East, they all get muddled. We have an interest in promoting our values. A Syria without Assad, like a Libya without Gadhafi or an Iraq without Saddam or an Iran without nuclear weapons, is a safer place for Americans as well as a healthier place for the locals.

However, when weighing the pros and cons of some potential use of U.S. military force in a distant land, we tend to credit our good intentions as if they had been realized. One lesson of recent interventions is that, even as the world’s greatest superpower, we aren’t very good at these things. We squeezed Iraq’s economy for a decade between the two Persian Gulf wars. How many innocent lives did that cost? Developments in military technology — such as drones — make intervention less costly in blood for us and thus possibly make it easier to contemplate. They do little to change the equation for the people we are sincerely trying to help.

Just Because

Intervention never will be, and maybe never should be, an all-or-nothing decision. There are goals that are worth attempting, but may not be worth giving our all for.

We will never have logically consistent rules about such things (to the frustration of people, including me, who tend to equate logical consistency with justice and good sense). To questions like, “Why Iraq but not Iran?” or, “Why are we standing by while a Syrian dictator tears apart his own country?” the answer is, “Just because.”

Decisions about using force will always be affected, if not determined, by extraneous factors. Is it an election year? How is the economy? Have there been a lot of these situations lately? All these considerations affect a decision whether to use military force even though they have nothing directly to do with it.

Too often, when we weigh the costs and benefits of some form of intervention, we take credit for our intentions, rather than the results. Whether the invasion and occupation of Iraq would have been worth the costs if we were leaving behind a stable democracy as promised is a very different question from whether the war was worth it as it actually turned out.

Michael Kinsley

Michael Kinsley is a Bloomberg View columnist.