In July, the Federal Aviation Administration prohibited U.S. airlines from flying to Israel's Ben Gurion Airport in Tel Aviv for 48 hours because a Hamas rocket landed about a mile away. It was the greatest victory the Hamas terrorists have ever achieved.

America's national security interest in defending Israel is recited often and loudly by the Obama administration, but its actions don't match its words. If America has a vital national security interest in defending Israel, shouldn't we be helping Israel defend a principal lifeline?

Some U.S. politicians such as Sen. John McCain, R-Ariz., seem preoccupied with bombing the Russian insurgents who shot down Malaysia Airlines Flight 17. Among politicians and analysts, there is only confusion about when military force should be used.

In a July 16 Washington Post column, neoconservative Robert Kagan sought to justify the interventionist theory of foreign policy by the number of times the United States has used military force since World War II.

Kagan began by writing that the Iraq War wasn't the greatest strategic error in recent decades, but the failure to take military action against al Qaeda and Osama bin Laden before Sept. 11, 2001, was. He wrote that America has undertaken some 26 armed interventions since the Spanish-American War. On the basis of that alone, Kagan asks us to conclude that frequent armed intervention is the American norm. He asks whether America should return to that norm from our present noninterventionist mood.

What is missing from Kagan's analysis — and from the fundamentals of neoconservatism — is a doctrinal theory of when American military force should be used. That is unsurprising because, as the godfather of neoconservatism, Irving Kristol, wrote in August 2003," ... there is no set of neoconservative beliefs concerning foreign policy, only a set of attitudes derived from historical experience." Those attitudes, he wrote, are that patriotism is good, world government is a bad idea and statesmen should be able to tell friends from enemies.

Like Kagan, Kristol prescribed no theory of defense and didn't define any rules for the use of military force, only implying that it should be used often: "With power come responsibilities, whether sought or not, whether welcome or not. And it is a fact that if you have the kind of power we now have, either you will find opportunities to use it, or the world will discover them for you."

But the use of military force — at the risk of our warriors' lives — should never be viewed as an "opportunity." Acts of military aggression are a commonplace in the world and, yes, U.S. military power is still unmatched. But there has to be a basis for judgment as to when it should be used.

What we can do is different from what we should do even pre-emptively. U.S. national security can be broken down into four essential elements:

1. Freedom of the seas

2. Freedom of the skies

3. Freedom of space

4. Freedom to operate in the cyberworld

Defending those freedoms should define our national security policy. For example, the shooting down of MH17 by Russian-backed insurgents threatened the freedom of the skies of Ukraine, but not ours. It would be a very different situation if they had shot down an American airliner or one of a NATO member nation. But they didn't. If we had a vital national security interest in protecting all civilian aircraft, we could have been justified in destroying all the SA-11 missile batteries in the possession of the Russian-backed insurgents in Ukraine. But we don't, so we wouldn't have been.

We shouldn't use military force there because no vital American national security interest is at stake. When President Obama decided to intervene militarily in Libya — against the advice of then-Defense Secretary Robert Gates — he made the wrong decision. As Gates advised him, there was no American national security interest in aiding France's campaign to oust Moammar Gadhafi. But Obama went ahead in disregard of our interests.

He has sent 100 Green Berets to search Uganda for Joseph Kony, the leader of the Lord's Resistance Army, and added reconnaissance drones and personnel to the mix. He did that because he could, in the absence of any American national security interest. Those actions fairly define the Obama Doctrine.

American military force should never be used except in the defense of vital national security interests. When one of our four freedoms is endangered, every U.S. president should consider military action to restore it.

Diplomacy, economic sanctions and the like are all options to be considered in response to any threat. But when one of America's four freedoms — or those of our allies — are threatened, it may be necessary to defend them with force.

Jed Babbin served as a deputy undersecretary of defense in the George H.W. Bush administration and is a senior fellow of the London Center for Policy Research. He is co-author with Herbert London of The BDS War Against Israel.