It looks as if we will be firing Tomahawk cruise missiles at Syria in the coming days, and critics are raising legitimate concerns: President Bashar Al Assad may escalate. Hezbollah may retaliate against Western targets. American missiles may kill civilians. A couple of days of missile strikes will offer merely a slap on the wrist that advertises the US’ impotence.

There is some truth to all that, but we also need to acknowledge something fundamental: President Barack Obama’s policy towards Syria has failed and it is time to try a tougher approach.

The war has spread and destabilised Lebanon, Jordan, Iraq and Turkey. The hardline Nusra Front rebels have gained strength. The Syrian army has won ground. Prolonged war has deepened sectarian hatreds that will make it harder than ever to put Syria back together.

I tend to be wary of the military toolbox, and I strongly opposed the Iraq war and the Afghan “surge”. But in conjunction with diplomacy, military force can save lives. We saw that in Bosnia and Kosovo under Mr Bill Clinton, and we saw that just this year in Mali.

The problem is that overcommitments in Afghanistan and Iraq have left Americans with society-wide post-traumatic stress disorder, so that they are wary of engaging in Syria at all.

But when I was last in Syria, in November, I met a grandma who had already lost her husband, her son and her daughter-in-law to the Assad regime. She was living in a leaky tent, and like everyone, was desperate for international support. “We ask for God’s help in ending this, and Obama’s,” she said.

What do we tell her? That we do not have the stomach to help her?

Granted, there is a legitimate question about whether a day or two of missile strikes against Syria (seemingly the most likely scenario) will deter Mr Assad from further use of chemical weapons. We cannot be sure, but to me that seems plausible.

Chemical weapons are of only marginal use, simply one more way to terrorise and demoralise opponents. Mr Assad has carefully calibrated his actions over the last few years, testing the domestic and international response before escalating.

At first, he merely arrested protesters. Next, his soldiers swept hostile neighbourhoods. Then, the Syrian army began firing rockets and mortars at rebel positions. Mr Assad moved on to indiscriminate bombing. Then, his army apparently used chemical weapons in small attacks. Finally, his army appears to have undertaken a major assault with nerve gas.

To me, there is some hope that destroying military aircraft or intelligence headquarters can persuade Mr Assad that chemical weapons are not worth the cost and that he is better off employing more banal ways to slaughter his people.

That is unsatisfying but would still be a useful message to other leaders. It would reinforce the international norm against weapons of mass destruction.

Are we making too much of chemical weapons? In Syria, a principal weapon of mass destruction has been the AK-47.

Yet, there is value in bolstering international norms against egregious behaviour like genocide or the use of chemical weapons. Since Mr Obama established a “red line” about chemical weapons use, his credibility has been at stake: He cannot whimper and back down.

Look, Syria is going to be a mess, whatever we do. The optimal window to intervene by supporting moderate rebels to achieve a quick end to the war may have closed. But if the coming clash gives us a chance to do more to arm certain rebel groups or share intelligence with them, that would still be worthwhile — all while backing the idea of a negotiated settlement.

For all the risks of hypocrisy and ineffectiveness, it is better to stand up inconsistently to some atrocities than to acquiesce consistently in them all. THE NEW YORK TIMES

ABOUT THE AUTHOR: Nicholas Kristof is a New York Times columnist and a winner of two Pulitzer Prizes. This is an excerpt of a longer commentary.