LOS ANGELES ― Since Syria’s civil war erupted, its large chemical-weapons arsenal has haunted the conflict zone and beyond. Now Israel says that chemical weapons have been used by the Syrian regime.

Escalating fears have driven U.S. President Barack Obama to declare repeatedly that any Syrian use or transfer of chemical weapons would cross a “red line,” for which President Bashar al-Assad’s regime would be “held accountable.” But the practical implications of this warning remain vague.

As dangerous as Syria’s chemical-weapons stockpile is, it pales in comparison with another risk that became evident in late February, when Syrian rebels overran a Scud-missile base in Al-Kibar, in the country’s remote northeastern desert. Beneath the installation lay the buried remnants of the North Korean-engineered nuclear reactor that Israel’s air force had destroyed on Sept. 6, 2007.

Had Israel not learned of the secret plant, which was on the verge of launching operations to produce material for an atomic arsenal, the rebels effectively would have been in possession of a radiological weapon. The mere threat could have held the Syrian government hostage. Far more worrying, had Syrian engineers built a lab at the site, or in other rebel-held territory, to extract plutonium from the reactor’s spent fuel, the insurgents might even have found themselves with the ingredients of an atomic bomb.

Fortunately, Syria does not face these threats today. But Pakistan, North Korea, and Iran ― all potentially unstable countries with growing nuclear enterprises ― may in the future. How concerned should the world be?

History provides grounds for optimism. After all, host countries have been able to contain nuclear risks in the most challenging circumstances. During Yugoslavia’s violent collapse, adversaries never struck or invaded Serbia’s research reactor, powered by weaponizable enriched uranium. When Serbian fighter jets flew threateningly low over Slovenia’s nuclear power plant, they spared the reactor.

Likewise, during China’s Cultural Revolution, the imposition of martial law prevented attempts by rival factions to seize nuclear facilities in Xinjiang and Qinghai. In 1961, as a group of former French generals revolted in French Algeria, an atomic-bomb test in the Sahara went off without a hitch. And, most significant, during the collapse of the Soviet Union, the vast nuclear arsenal remained intact.

However, concern that the Syrian government could intensify its use of chemical weapons against rebel-held areas, or that rebels could initiate attacks or respond with captured chemical weapons, raises questions about the pattern’s durability and the international community’s reaction.

The United States, which has become the world’s leader in containing the chemical-weapons risk, seems befuddled. Early last year, the U.S. Department of Defense let it be known that 75,000 troops would be needed to secure Syria’s chemical facilities. After the wars in Afghanistan and Iraq, it is not surprising that this estimate did not exactly generate a groundswell of public support for military intervention in Syria.

Recent statements from U.S. officials have not been reassuring. In January, then-Secretary of Defense Leon Panetta said that the U.S. was not pursuing options that involve “boots on the ground” to secure Assad’s arsenal during the conflict. At the same news conference, Martin E. Dempsey, chairman of the Joint Chiefs of Staff, conceded that preventing the Syrian government’s use of chemical weapons would require such clear, comprehensive intelligence that obtaining it is “almost unachievable.” Appearing before the Senate Armed Services Committee on April 17, Dempsey added that he had no confidence that U.S. forces could secure the arsenal given the number of sites.

Such remarks from senior military authorities suggest that Obama’s warnings may be hollow. Worse, they inspire little confidence that the U.S. can deal with future cases in which countries with nuclear assets find themselves in revolt, civil war, or political collapse ― and with compromised domestic atomic safeguards risking the spread of nuclear havoc to other regions.

Such risks demand examination and planning. But, to rely on the U.S. government alone to plot the most effective strategy in the shadow of possible internal group-think is asking too much. Outside vetting ― including published reviews by congressional investigative bodies, think tanks, and scholars ― could add important insights.

In the aftermath of America’s poorly executed recent wars and confounded planning with respect to Syria’s chemical weapons, such vetting is the least that Americans and their allies should expect in order to prevent the realization of the sum of all our fears: the first nuclear attack or intentional major radiological event of the twenty-first century.

By Bennett Ramberg

Bennett Ramberg served in the Bureau of Politico-Military Affairs under George H. W. Bush, and is the author of several books on international security. ― Ed.

(Project Syndicate)