President Obama’s on-and-off-again planned American attack on Syria is nothing new. Besides its five declared wars, America has a habit of intervening all over the world.

The roll call of recent US military interventions is astounding: Cambodia, Iran, Libya, Lebanon, Grenada, Panama, Liberia, Iraq, Haiti, Somalia, the former Yugoslavia, Zaire and Afghanistan.

Even the notion of past American isolationism is a myth. In the four years between 1912 and 1916 alone, the United States sent troops into Cuba, Panama, Honduras, Nicaragua, Mexico, the Dominican Republic and Haiti.

Even those busy years of intervention were not novel. Since our infancy, the US military has been constantly engaged. In another four-year period between 1812 and 1816, America fought the British, the French, the Spanish and the North Africans.

Some of these deployments were effective, either furthering US and allied interests or serving a common humanitarian purpose. Greece was saved from communism after World War II. Saddam Hussein was forced out of Kuwait and ultimately Iraq. Dictator and drug-dealer Manuel Noriega was deposed from Panama. At other times, our periodic undeclared wars just made things worse.

With President Obama contemplating bombing Syria, is there any guide from the past about whether this attack is wise?

Sometimes the president sought congressional approval (e.g., both Bushes in the two Iraq wars). At other times he attacked without authorization (Clinton in the Balkans). Obtaining a UN resolution seemed wise before the first Gulf War, but proved impossible in the Balkan bombing.

After Vietnam and the passage of the War Powers Act, it was more likely for a president to seek congressional authorization, but again not always. President Ronald Reagan bombed the Libyans and invaded Grenada without asking Congress.

Sometimes the undeclared interventions cost Americans tens of thousands of lives (Korea and Vietnam). But often, very few were killed (Panama and Grenada). The interventions could last just a few days, as when Clinton sent missiles and bombs into Afghanistan, East Africa and Iraq, or years on end like the costly ground fighting in Afghanistan, Iraq and Vietnam.

If we collate all the interventions since the Marines invaded Tripoli in 1804, a certain pattern emerges. The more clearly defined and decisive the intervention, the more likely it was judged successful. And making progress or winning outright was essential to ensuring public support

Even disastrous and ill-thought-out interventions that achieved nothing or made things worse, such as President Gerald Ford’s 1975 attack in Cambodia, President Jimmy Carter’s failed Iran rescue mission (1980) or Reagan’s intervention in Lebanon (1982-’83) didn’t cause lasting popular outrage — given that setbacks were brief and the operations quickly ended.

In contrast, any war that drags on and costs thousands of American lives — in Afghanistan, Iraq, Korea, the Philippines or Vietnam — proves unpopular, even when they sometimes succeed in deposing tyrants and putting something better in their place.

We shouldn’t expect much good from bombing Syria, given the difficulty to sort out the various insurgents and our loud prior announcements of limiting the use of force.

To the degree we aren’t willing to insert ground troops, it is more likely both that we won’t accomplish much and won’t get trapped in a quagmire.

It is wiser to obtain congressional approval, and the more foreign allies that join the better. Having a clear objective, a sound methodology and a definition of victory is essential, whether in big or small interventions.

But so far Obama can’t decide on the real objective in Syria, much less how to obtain it. Is the goal the elimination of WMDs, to punish Bashar al-Assad for using these weapons, to restore the president’s credibility after issuing red lines, immediate US national-security interests, Assad’s removal or help to the insurgents?

If Obama neither obtains congressional approval nor attempts to go the UN, the attack will probably be unpopular abroad — even more so without any allies or US public support.

Finally, promising in advance that whatever we do will probably be short and limited will make it likely that, if it fails, it will be forgiven and forgotten — and if deemed successful, it will have little, if any, lasting, strategic effects.