The images emerging from Syria — from this hysterical young girl to those rows of corpses — should be a turning point in a conflict that is rapidly destabilizing the Middle East. The chemical weapons attack, if proven, demonstrates either the depravity of Bashar al-Assad — or the rebels fighting him.

But President Obama is reacting with the same split-the-difference caution that handicaps his administration’s efforts in so many other areas. In an interview on CNN Friday morning, Obama essentially said he will not be George W. Bush.

“The United States continues to be the one country that people expect can do more than just simply protect their borders,” he said. “But that does not mean that we have to get involved with everything immediately. We have to think through strategically what’s going to be in our long-term national interests.”

Clearly, the United States should not invade Syria. Deploying American ground troops would be disastrous. But the worst chemical weapons attack in 30 years, if proven, should be a watershed moment. Dictators and terrorist groups must be shown that the use of weapons of mass destruction comes at a price. 

If the Syrian government is found to be responsible for the attack, the administration and its European allies should carry out cruise missile and airstrikes to punish Assad’s military. And if the Syrian opposition is found to have carried out an attack on its own people, all Western support to the rebels should end. 

The conflict has killed more than 100,000 people and is growing worse, not better. Earlier this month, CIA officials said that Syria’s mix of al-Qaida-aligned militants and chemical weapons is the single largest security threat the United States faces. Syria’s descent is inflaming sectarian tensions across the region and destabilizing Lebanon and Iraq as well.

It is too late to end the war. The short-term goal should be to punish Assad, not remove him from power. A long-term White House review of U.S. strategy in Syria and the region should also be carried out.

Americans understandably want to avert their eyes from Syria and the Middle East, with 1,000 dead in Egypt and car bombs routinely killing dozens in Iraq. But a mass chemical attack is chillingly different.

International law and human decency bars the use of chemical weapons. If 500 to 1,300 people died, as rebels allege, the killings in Damascus would be the worst chemical attack since Saddam Hussein gassed the Kurds in the 1980s. If there was ever an incident that crossed President Obama’s chemical weapons “red line,” this it.

On Thursday, French Foreign Minister Laurent Fabius said that the West would have to respond militarily if evidence confirms a government attack.

“There would have to be reaction with force in Syria from the international community,” Fabius said.

Questions surround what happened. Israeli officials said they believed a chemical attack had occurred but they did not know the perpetrators.

The timing is also odd. The deaths occurred three days after the arrival of a 20-member United Nations chemical weapons inspection team that the Syrian government had blocked for months. And it unfolded a mere 15-minute drive from where the U.N. team was staying. As Patrick Cockburn rightly noted in the Independent, both sides are also fighting a propaganda war.

Depending on who carried it out, the attack signifies vastly different things. Assad could be boldly defying a West that he is convinced will not respond. Rebels could have carried out the attack in a scurrilous attempt to spark an intervention. And the images, of course, could be fake.

In what has now become a predictable pattern, Russian and Chinese officials blocked an effort by American and European officials to enact a U.N. Security Council resolution calling for an immediate investigation. Instead, a much-more watered-down version passed. 

In a positive sign on Friday, Russian officials called on both the Syrian government and rebels to allow U.N. inspectors to investigate the attack. It is vital for American, European and U.N. officials to continue to pressure the Russians and Assad to grant access.

In the days ahead, the White House will have limited control of whether or not U.N. inspectors gain access to the site of the attacks. But it will have total control of its messaging.

If Obama does not plan to act militarily, he should admit we have no “red lines.” If we plan to do nothing, we should stop making empty threats. That is more honest to Americans, Syrians and Damascus’ newest dead.

Maine native David Rohde is a columnist for Reuters, a two-time winner of the Pulitzer Prize, and a former reporter for The New York Times and Christian Science Monitor.