The anonymous series of announcements coincided with remarks President Obama made on counterterrorism policy at National Defense University in which he called for "transparency and debate on this issue." A classified Presidential Policy Guidance on the matter, issued at the same time, caught some in government by surprise, triggering a scramble at the Pentagon and at CIA to achieve a White House objective. The transfer was never expected to happen overnight. But it is now clear the complexity of the issue, the distinct operational and cultural differences between the Pentagon and CIA and the bureaucratic politics of it all has forced officials on all sides to recognize transferring drone operations from the Agency to the Defense Department represents, for now, an unattainable goal.

"The physics of making this happen quickly are remarkably difficult," one U.S. official told FP. "The goal remains the same, but the reality has set in."

Officials at the CIA and the Defense Department are loathe to try and fix a program that they don't think is broken, even if it has become a political liability for Obama, who has faced constant pressure from human rights activists, his political base, and a growing chorus of libertarian Republicans to scale back the program and subject it to greater public scrutiny. But the pitfalls of transferring operations reside in more practical concerns. The U.S. official said that while the platforms and the capabilities are common to either the Agency or the Pentagon, there remain distinctly different approaches to "finding, fixing and finishing" terrorist targets. The two organizations also use different approaches to producing the "intelligence feeds" upon which drone operations rely. Perhaps more importantly, after years of conducting drone strikes, the CIA has developed an expertise and a taste for them. The DOD's appetite to take over that mission may not run very deep.

The military operates its own drones, of course, and has launched hundreds of lethal strikes in Iraq and Afghanistan. But the CIA is more "agile," another former official said, and has a longer track record of being able to sending drones into places where U.S. combat forces cannot go.

"The agency can do it much more efficiently and at lower cost than the military can," said one former intelligence official. Another former official with extensive experience in intelligence and military operations said it takes the military longer to deploy drones -- in part because the military uses a larger support staff to operate the aircraft.

The military also cannot conduct overt, hostile action in Pakistan, where the drones have been most active and are practically the only means the United States has to attack terrorists and militants in remote regions. Yes, the pace of strikes has significantly decreased since the 2010 peak of an estimated 122 unmanned attacks in Pakistan. But the drones are most certainly still flying. Last week, a drone strike killed the leader of the Pakistani Taliban, Hakimullah Mehsud, who had a $5 million U.S. bounty on his head for his involvement in a 2009 attack in Afghanistan. Over the summer, a spate of drone strikes killed a dozen militants in Yemen.

Keeping the drones with the CIA also offers legal cover for drone strikes, former officials argued. By law, the military is not supposed to conduct hostile actions outside a declared war zone, although special forces do so on occasion acting at the CIA's behest.

When the White House began floating the idea earlier this year of transferring the drone program to the military, some lawmakers were skeptical, said a former U.S. official. John Brennan -- the White House counterrorism czar turned CIA director -- might have allegedly grown uncomfortable with the targeted killings that he helped oversee for so long. But the congressmen doubted whether the government of Pakistan would ever allow drone strikes run by the U.S. military to occur in their country.

"That was the president's aspirational goal, but no one ever believed the Pakistanis were going to let us do that," said the former official, who was involved in discussions over transferring the drone program to the military.

For years, the Pakistani government has given tacit approval to CIA-led strikes. But they were conducted as covert actions under U.S. law, meaning they were never officially acknowledged by U.S. officials. That gave the Pakistanis some wiggle room to tell an angry public, which would never tolerate American troops on the ground, that Pakistani leaders had nothing to do with the strikes on their territory.

Even though Obama and other senior U.S. officials now publicly discuss CIA drone strikes, they are still conducted as covert operations. In practical terms, that means it's extremely difficult for journalists and outside researchers to obtain data from the CIA about its drone operations. And they are still briefed to Congress as covert operations, so relatively few lawmakers and congressional staff know about them.

The secrecy of drone operations could have far reaching effects on U.S. foreign policy as other nations build and deploy their own drone fleets.

"We are setting precedent that other nations will follow," said Micah Zenko, a fellow with the Council on Foreign Relations who closely follows the CIA drone program. "If the executive branch wants maximum authority with this very minimal amount of transparency and limited-in-scope oversight, that's a precedent that other countries will look to as well."