NEW YORK - Classified documents leaked to The Intercept by an intelligence source published Thursday provide an unprecedented look at a secret drone-based assassination program of the U.S. military that has spanned four presidential terms and two commanders-in-chief.  “The Drone Papers” offer the public rare primary source documents detailing the kill/capture program, giving a never-before-seen look into the military’s secret drone war in Yemen and Somalia and providing new details on a controversial campaign in Afghanistan.

The leaked documents show that operations in Yemen and Somalia have relied on dubious intelligence, that the number of people killed is far greater than the number of people on the target list, and that overreliance on drone attacks hampers the ability of U.S. forces to extract potentially valuable evidence from terror suspects.

An intelligence community source that worked on the drone program provided the classified slides to The Intercept, which granted the source’s request for anonymity because the material is classified and the U.S. government has aggressively persecuted whistleblowers. A team of reporters and researchers spent months analyzing the documents, and Thursday published a multimedia package of eight stories that presents an extensive overview of the so-called “targeted killing” program. Among the key revelations in the series:

• Assassinations have depended on unreliable intelligence. More than half the intelligence used to track potential kills in Yemen and Somalia was based on electronic communications data from phones, computers, and targeted intercepts (know as signals intelligence) which, the government admits, it has “poor” and “limited” capability to collect. By the military’s own admission, it was lacking in reliable information from human sources.

• The documents contradict Administration claims that its operations against high-value terrorists are limited and precise. Contrary to claims that these campaigns narrowly target specific individuals, the documents show that air strikes under the Obama administration have killed significant numbers of unnamed bystanders. Documents detailing a 14-month kill/capture campaign in Afghanistan, for example, show that while the U.S. military killed 35 of its direct targets with air strikes, 219 other individuals also died in the attacks.

• In Afghanistan, the military has designated unknown men it kills as “Enemies Killed in Action.” According to The Intercept’s source, the military has a practice of labeling individuals killed in air strikes this way unless evidence emerges to prove otherwise.

• Assassinations hurt intelligence gathering. The Pentagon study finds that killing suspected terrorists, even if they are legitimate targets, “significantly reduce[s]” the information available and further hampers intelligence gathering.

• New details about the ‘kill chain’ reveal a bureaucratic structure headed by President Obama, by which U.S. government officials select and authorize targets for assassination outside traditional legal and justice systems, and with little transparency. The system included creating a portrait of a potential target in a condensed format known as a ‘Baseball Card,’ which was passed to the White House for approval, while individual drone strikes were often authorized by other officials.

•  Inconsistencies with publicly available White House statements about targeted killings. Administration policy standards issued in 2013 state that lethal force will be launched only against targets that pose a “continuing, imminent threat to U.S. persons,” however documents from the same time reveal much more vague criteria, including that a person only need present “a threat to U.S. interest or personnel.”

• New details of high-profile drone kills, including the 2012 killing in Somalia of Bilal al-Berjawi, which raise questions about whether the British government revoked his citizenship to facilitate the strike.

• Information about a largely covert effort to extend the U.S. military’s footprint across the African continent, including through a network of mostly small and low-profile airfields in Djibouti and other African countries.

“It’s stunning the number of instances when I’ve come across intelligence that was faulty, when sources of information used to finish targets were misattributed to people,” the source said to The Intercept. “And it isn’t until several months or years later that you realize that the entire time you thought you were going after this target, it was his mother’s phone the whole time. Anyone caught in the vicinity is guilty by association – it’s a phenomenal gamble.”

The decision to leak the documents was made because the process by which people are placed on kill lists was, “from the very first instance, wrong,” the source said. “We’re allowing this to happen. And by ‘we,’ I mean every American citizen who has access to this information now, but continues to do nothing about it.”

The documents contradict assurances from the Obama administration that drone strikes are a more precise alternative to boots on the ground and are authorized only when an “imminent” threat is present. The documents show the ways in which “imminence” has been redefined to bear almost no resemblance to its common-sense definition.

The slides were produced during a key time in the evolution of the drone wars—between 2011 and 2013—and provide context as the U.S. military intensifies drone strikes and covert actions against ISIS in Syria and Iraq. Many of them contain internal views on the shortcomings of the drone program. One study by a Pentagon entity -- the Intelligence, Surveillance and Reconnaissance Task Force -- lamented the tendency to kill suspected terrorists over capturing and interrogating them, arguing for more advanced aircraft and expanding the use of naval vessels to extend the reach of surveillance operations.

“Privately, the architects of the U.S. drone program have acknowledged its shortcomings,” said Betsy Reed, Editor in Chief of The Intercept. “But they have made sure that this campaign, launched by Bush and vastly expanded under Obama, has been shrouded in secrecy. The public has a right to know how the US government has decided who to kill.”