The 5 biggest US intelligence leaks

A stockpile of documents that reportedly leaked from the Pentagon have surfaced online over the past week, appearing to give insight to NATO intelligence in the Ukraine war, leaving Western defense officials scrambling to find the source. 

While some have pointed to the possibility that the Russian government or pro-Russian sources are responsible for the leak, no concrete conclusion has publicly been made. Instead, defense officials have demurred on even confirming the authenticity of the documents, which provide estimates of the casualties in the war and details on the training of Ukrainian forces.

The high-profile leak is one of the most wide-ranging breaches of defense information in the U.S. in a decade and points a spotlight on military secrets that, while occasionally are revealed in small doses, largely remain under wraps in the Pentagon and defense industry.

Here are five of the largest intelligence leaks that have rocked Washington in U.S. history.

Edward Snowden’s NSA leaks

In 2013, the leaks from Edward Snowden, an intelligence community insider, revealed bombshell details about the U.S. government’s actions in covertly surveilling millions of Americans.

The surveillance program came in the wake of the 9/11 attacks, with government officials seeing a need to beef up security programs and surveillance operations to scope out potential criminal and terrorist threats. The leaks from Snowden, however, revealed that the government was collecting information from regular citizens, not just potential terrorist threats.

The revelations from Snowden, a National Security Agency (NSA) contractor who later fled to Hong Kong and eventually Russia and was federally charged with the theft of government property and other offenses, also revealed U.S. programs to spy on foreign governments. The leaks showed that the American government bugged a number of European Union offices and spied on at least 38 foreign embassies.

The highly-classified documents that were leaked by Snowden, who is viewed by some as either a brave whistleblower or a government traitor, ushered in newfound angst for Americans over their digital footprint and personal data, a fight that is still playing out today.

The Pentagon Papers

A top-secret Defense study into the U.S. involvement in the Vietnam war, which grew increasingly unpopular as the conflict dragged on into the 1970s, was leaked to The New York Times in March 1971. The resulting reporting by the Times unleashed a hailstorm on the federal government, detailing the country’s decades-long involvement in Vietnam and validating many of the anti-war criticisms.

The documents, which detail U.S. policy decisions and deliberations between 1945 to 1967, were leaked to the Times by Daniel Ellsberg, a military analyst who secretly photocopied the report and gave it to reporters.

The papers were damning, including the steps by successive U.S. presidents, including Harry Truman, Dwight Eisenhower, John Kennedy and Lyndon Johnson, to covertly and overtly accentuate conflict in the region.

The leak was a major blow to the U.S. military and political structure, peeling back details that officials had worked to keep secret for years.

It also resulted in one of the most monumental fights between the federal government and the press, after the Justice Department secured a temporary injunction against the publication of the reports. At the end of June 1971, the Supreme Court allowed the Times and The Washington Post to continue publishing the reports in a 6 to 3 decision, still widely regarded as one of the most consequential cases for press freedom in U.S. history.

Iraq war logs

WikiLeaks, a media organization founded by Julian Assange, published a trove of leaked classified military documents in 2010 detailing the actions of U.S. and coalition forces in the Iraq war from 2004 to 2009. The leaks provided one of the most sobering looks into the conflict at that point.

The leaks revealed a number of disturbing dynamics in the war, including the number of civilians who had died. By 2009, the leaks revealed that 66,000 civilians, compromising more than 60 percent of the deaths in the war, had died. It also showed that hundreds of those civilians were killed by coalition forces. Thousands of those civilian deaths had yet to be reported publicly.

The documents also allege prison abuse, even after the widely reported abuse of detainees at the Abu Ghraib prison in the early stages of the war. They also concluded that U.S. forces had handed over prisoners to an Iraqi group known for widespread torture tactics. 

The leaks comprise nearly 400,000 reports, or logs, recorded by soldiers on the ground in the war.

The leak helped sink public support for the war, which had already been waning after the initial decision to invade the country in 2003. By the time President Obama announced plans to end U.S. military operations in Iraq in 2011, 75 percent of respondents fully approved of the decision to wind down the war, according to a Pew Research poll.

Robert Hanssen’s espionage career

In 1976, Robert Hanssen joined the FBI as a special agent. Throughout his 25 years in the FBI and law enforcement, he spied on the U.S. government for the Soviet Union and Russian intelligence services.

Throughout the Cold War, Hanssen acted as a spy for the Soviet Union, going undetected for years before being suspected by officials in the mid-1980s. Given his stature in the bureau, Hanssen had access to classified information, selling thousands of pieces to Soviet and Russian sources, detailing U.S. military plans, strategies in the event of nuclear war and weapons technologies. He reportedly made around $1.4 million in cash and diamonds from selling the intelligence information.

In 2000, law enforcement secured Russian information that pointed to Hanssen being the spy. Right on the verge of retirement, investigators caught Hanssen in the act of conducting a drop of classified information for Russian sources at a park in Virginia and arrested him. 

Hanssen eventually pleaded guilty to 15 counts of espionage later that year; he is serving 15 consecutive life sentences without parole in a prison in Colorado.

Ukrainian war leak

The most recent leak of what is reportedly NATO documents pertaining to the war in Ukraine is one of the largest military and intelligence breaches in U.S. history. 

While officials have yet to confirm the authenticity or source of the leaks, the documents do provide an interesting insight into the war in Ukraine. With the possibility that they were leaked from a Russian source, some have pointed out that some of the information may have been altered.

Nevertheless, it details U.S. and Western support of Ukraine, including the progress of arms aid. The documents also seem to reveal that the U.S. has been spying on both Russian and Ukrainian leaders to monitor the war, according to The New York Times. They also detail how the U.S. tracks Russian military movements with satellites, according to the Times.

One thing it does not reveal, though, is plans for a renewed Ukrainian counteroffensive, which has widely been rumored after Russia launched an offensive in late winter that has largely stalled.