Max Boot is a senior fellow in national security studies at the Council on Foreign Relations and the author of “Invisible Armies: An Epic History of Guerrilla Warfare from Ancient Times to the Present,” due out in January.

It’s easy to tell when the Pentagon is opposed to a military intervention. That’s when we hear leaks saying how difficult such action would be. We heard them in the 1990s concerning Bosnia and Kosovo, we heard them last year over Libya, and we are hearing them now about Syria.

News reports cite unnamed “senior defense officials” saying that Syria has a sophisticated air-defense system and a 330,000-man army that would be hard to defeat; that we don’t know enough to arm a Syrian opposition that lacks effective, unified leadership; that U.S. intervention could plunge Syria into civil war and embroil us in a “proxy war” against Iran and possibly Russia; and that international support is lacking for any move.

All of this is supposed to preclude a range of actions, including arming the Syrian opposition, enforcing “no-fly” zones, launching air strikes on regime targets and setting up humanitarian corridors where Syrians could seek refuge from a regime that has killed probably at least 10,000 civilians.

It is understandable, and laudable, that military leaders are reluctant to send their troops into harm’s way. And just because defense officials tend to cry wolf doesn’t mean that they are always wrong or that their warnings should be disregarded. Obviously, the George W. Bush administration should have listened more carefully to skeptics inside and outside government before the invasion of Iraq — even though senior military leaders signed off on every bad decision.

Today, in the case of Syria, any military action needs to be carefully thought through, but we should not refuse to act simply because of the worst-case scenarios being raised by the Pentagon.

Start with Syria’s supposedly formidable air defense. Given the ease with which Israel penetrated those defenses in 1982, during the Lebanon War, and in 2007, to take out the al-Kibar nuclear reactor, it is unlikely that the systems would pose that much of a challenge to the world’s most sophisticated and powerful air force.

The U.S. Air Force had no trouble taking out Saddam Hussein’s air defenses on two occasions, and those, like Syria’s, were constructed largely on the Russian model.

And what about that 330,000-man army? Most of the soldiers are poorly trained and unmotivated Sunni conscripts unwilling to do much to defend a regime dominated by Alawites, an offshoot of Shiite Islam. Bashar al-Assad’s regime can count on only about 30,000 Alawite soldiers, which is why the same units are used to attack one rebel stronghold after another.

The potential for starting a “proxy war” with Iran or Russia should be even less worrisome. Iran has been waging war — sometimes by proxy, sometimes directly — against us since taking our embassy personnel hostage in 1979. If we were to help topple Tehran’s allies in Damascus, it would be merely a belated counterattack for all of Iran’s aggression against the United States.

As for Russia, yes, Moscow has a naval station in Syria, but presumably U.S. aircraft would not target Russian facilities. Short of that, it’s hard to see how anything we might do would start any kind of conflict with Russia. This isn’t the Cuban missile crisis, and Russia would not go to war to defend the Assad regime.

What about the fractured nature of the Syrian opposition? That’s a real concern — but one that could be alleviated by the provision of training and aid. U.S. personnel could play a critical role by using our largess to buttress the more moderate elements of the opposition while shutting out factions affiliated with extremist groups that receive support from Gulf Arabs. So far, however, news accounts suggest that we have not yet even provided communications equipment that the rebels could use to coordinate activities.

Aiding the rebels would hardly risk plunging Syria into civil war. Syria is already in a civil war, and it is getting worse. The more pressure we bring to topple Assad, the faster we can end that war and the more influence we can exert with a successor regime.

By contrast, if we stand on the sidelines, worst-case scenarios — such as Syrian chemical weapons falling into the wrong hands or groups such as al-Qaeda developing havens — are more likely to result because of the Assad regime’s inability to control its own territory.

The need for a coalition is real, but plenty of international opposition has been raised to the Assad regime. Notwithstanding the lack of a U.N. resolution — blocked by Russia and China — Washington could assemble a coalition of the willing as President Bill Clinton did for Kosovo. But that will happen only if the Obama administration decides that action is called for and does not allow itself to be paralyzed by the Pentagon’s reluctance to intervene.