In Syria, the United States is focused on countering the self-declared Islamic State, or ISIS. But what strikes terror among perhaps even more Syrians are the indiscriminate, so-called barrel bomb attacks by government forces.

Barrel bombs are crude metal drums packed with explosives and shrapnel. They are dropped off the hatch of helicopters and have the power to pulverize an entire block. Syrian activists have filmed hundreds of attacks and posted the videos online.

Images of the aftermath show residential buildings reduced to pancaked layers of concrete slabs. Rescue teams struggle to save those trapped beneath tons of cement, often finding the victims mangled beyond rescue.

A Devastating Weapon Of Choice

The attacks have killed nearly 14,000 people, according to the Syrian Network for Human Rights, an anti-regime rights watchdog. Roughly half of the victims came after a United Nations Security Council resolution demanded an end to indiscriminate barrel bomb attacks on civilians.

Now, human rights activists are making a new push to bring attention to the ongoing attacks and to ratchet up pressure on the international community to stop them. That effort has gained traction at the Security Council, where a French-sponsored draft resolution is in the works to monitor violations and open the possibility of sanctioning the perpetrators.

The U.S. ambassador to the U.N. Samantha Power called earlier this month to put an end to what she says seems to be the regime's "weapon of choice" against civilians.

Syrian President Bashar Assad has denied that his forces use barrel bombs at all. Yet, the regime is the only party with the helicopters to drop them.

New York-based Human Rights Watch has been documenting the barrel bomb attacks using satellite imagery and witness testimony. The watchdog is working to ratchet up pressure on Assad's allies, Russia and Iran, as well as his foes, including the U.S., in hopes of stopping the indiscriminate attacks.

Director Kenneth Roth notes that there are legitimate reasons why the Syrian air force flies, such as bombing military targets or resupplying pro-government areas besieged by rebels. But the barrel bombs are "so imprecise that the military doesn't dare drop them on the front lines for fear of hitting its own troops."

Human Rights Watch says the regime is using barrel bombs to decimate schools, residential buildings and even medical facilities, in direct contravention of the Geneva Conventions. Roth says the campaign is part of a total-war strategy designed to drive civilians from rebel-held territory.

'Where The Planes Don't Fly'

One woman who has so far refused to leave Syria's rebel-held territories is Muzna Jundi. When rebels drove regime troops from her home city of Maaret al-Numan in November 2012, Jundi started a women's center, offering everything from French courses to psychosocial support to hairdressing courses. But the "liberation" of her city came at a great price: a relentless campaign of barrel bomb attacks, sometimes more than 20 per day.

"I'm sure 95 percent of the targets are civilian. Civilians only. Okay?" she says, her voice quivering over Skype. The attacks have decimated the city's population. Jundi says nearly half of the original 120,000 residents have fled, whether north to Turkey or to government areas "where the planes don't fly."

Jundi says that government airstrikes are her sole daily concern, and she wants the international community to enforce a no-fly zone to stop them.

A no fly zone has been a key demand of Syrian opposition groups since the uprising was met with a fierce crackdown by government forces in 2011.

But with the United States and its allies focused on the war against ISIS, that goal has never been further off. Pentagon officials have said a no-fly zone would cost billions, and could risk the downing of U.S. warplanes without stopping the war.

Scott Cooper, a former U.S. marine aviator who is writing a book about his experience enforcing no fly zones over Bosnia and Iraq, says that the technical challenge of a Syria no-fly zone is quite feasible. It could even be done without planes; using radar monitoring and Patriot missile systems instead.

But Cooper cautions that as long as Iran and Russia continue to support the Assad regime, a no-fly zone absent a larger political vision would only shift battlefield dynamics.

"Quite honestly you could save some civilians with a no-fly zone," he says. "But if it's absent a larger strategy to engage and figure out what a post-Assad regime looks like, it's probably not going to do a whole lot of good."

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