© Getty Images

The Manhattan Project -

The Manhattan Project is perhaps the most well-known secret operation of the American government, in no small part due to its devastating consequences. Started in 1939 and led by Robert Oppenheimer, the Manhattan Project was started to investigate the possibility of weaponizing atomic energy, and that hypothesis was quickly proven true.

© Getty Images

The Manhattan Project -

In August 1945, two atomic bombs were dropped on the Japanese cities of Hiroshima and Nagasaki, proving to the world that atomic energy could in fact be weaponized and used to cause incomprehensible suffering.

© Getty Images

Project 1794 -

It was a great day for UFO enthusiasts when, in 2012, the US government declassified a host of papers documenting their own plans to build a flying saucer. While the government-issued saucer wouldn’t be used for extra-terrestrial ambitions, it would be a secret weapon used in the fight against the Soviets.

© Getty Images

Project 1794 -

Project 1794 began in the 1950s, and didn’t last very long. The proposed aircraft had some lofty goals to live up to, such as having a top speed four times the speed of light, a maximum altitude of 100,000 feet (30,480 m), and an estimated price tag of US$26 million. In 1961, after some preliminary tests, it was decided that the technology simply wasn’t there yet.

© Getty Images

Project MK-Ultra -

Known as MK-Ultra, this project was the government’s extensive investigation into the uses of mind-altering substances and their ability to hypnotize soldiers and citizens. Started in 1953 and led by Sydney Gottlieb, the project used at least US$10 million ($87.5 when accounting for inflation) of taxpayer dollars to study the effects of various chemicals, specifically LSD, on unsuspecting subjects.

© Public Domain

Project MK-Ultra -

Numerous CIA agents as well as members of the general public were administered the drug without their informed consent, a direct violation of the Nuremberg Code. One victim, a patient in a Kentucky mental institution, was given LSD every day for 174 days.

© Public Domain

Operation Paperclip -

After World War II, the allyships that helped win the war and defeat the Nazis quickly dissolved with the start of the Cold War, which saw the United States and the Soviet Union move swiftly from allies to enemies.

© Public Domain

Operation Paperclip -

One of the more questionable and little-known strategies devised by the American government was known as Operation Paperclip, in which they rounded up all of the very best Nazi scientists that weren’t tried in the Nuremberg Trials and offered them jobs within the US government. Many of these individuals, including high-ranking member of the Nazi party Wernher von Braun, would go on to work with NASA on their space program.

© Getty Images

Project Mockingbird -

Project Mockingbird was a warrantless wiretapping operation carried out on the orders of President John F. Kennedy between March and June of 1963.  It was kept under wraps until 2001.

© Getty Images

Project Mockingbird -

The initial target of the wiretaps was New York Times reporter Hanson Baldwin, who had gotten on the president’s bad side for putting confidential information comparing the atomic arsenals of the United States and the USSR in an article. However, over the course of the operation, two other newsmen were also targeted.

© Getty Images

Operation Washtub -

Shortly after the start of the Cold War, the United States started putting safeguards in place in the event of a Soviet invasion on American soil. One of these safeguards, started in the early 1950s, was dubbed Operation Washtub.

© Public Domain

Operation Washtub -

Operation Washtub consisted of secretly organizing a number of ordinary Alaskan citizens into a group of spies, decoders, and potential resistance fighters. These “stay-behind” groups were commonly set up by the CIA and NATO around Europe, but the Washtub group is the only one of its kind known to exist on American soil.

© Getty Images

Acoustic Kitty -

This Cold War-era CIA scheme was playfully nicknamed Acoustic Kitty, and had all the makings of a revolutionary new surveillance system. Acoustic Kitty came about in the 1960s, and involved surgically placing a tiny microphone within a cat’s ear canal, and sending the felines out on patrol near Soviet embassies.

© Getty Images

Acoustic Kitty -

Predictably, the cats weren’t great at following orders, and after the first four-legged agent was almost immediately hit by a taxi and another few wandered away from the objective, the project was sacked.

© Getty Images

The kidnapping of Luna 3 -

By the 1960s, the Space Race was well underway, and the Soviet Union was in the lead. In 1959, from a remote base in Kazakhstan, they had successfully launched a rocket, Luna 3, towards the Moon, where it became the first spacecraft to reach and photograph the dark side of the Moon.

© Public Domain

The kidnapping of Luna 3 -

Once Luna 3 came back to Earth, the Soviets sent it on a publicity tour. The CIA, who felt it imperative to learn everything they could about this groundbreaking satellite, broke into the truck transporting the rocket under cover of night and proceeded to disassemble it completely, take photographs of each and every component, and reassemble the spacecraft before sunrise. Apparently, the Soviet Union never found out. At the time...

© Public Domain

The redistribution of 'Doctor Zhivago' -

Art and literature have always been among the most valuable weapons in a culture war. Because of this, books can be banned for any number of reasons. In the Soviet Union, numerous books were banned and authors were censored for being “anti-revolutionary” or dangerously individualistic. One of these books that was banned during the Cold War was the Russian classic 'Doctor Zhivago,' by Boris Pasternak (pictured).

© Getty Images

The redistribution of 'Doctor Zhivago' -

The CIA had read 'Doctor Zhivago,' and agreed with the USSR that it was in fact dangerously individualistic, and saw value in its use as anti-revolutionary propaganda. With the help of Dutch publishers and diplomats from the Vatican, the CIA printed and distributed around 1,000 copies of the novel at the 1958 World’s Fair in an attempt to embarrass the USSR.

© Public Domain

Operation Mongoose -

If there’s one thing the CIA is notorious for above everything else, it’s deposing foreign leaders. During the 1960s, the agency especially prioritized the assassination or removal from office of Cuban revolutionary leader Fidel Castro. Under the code name Operation Mongoose, a slew of failed assassination attempts were carried out between 1961 and 1963.

© Getty Images

Operation Mongoose -

Operation Mongoose accounted for many of the known 600-plus attempts on Castro’s life. Some of the more creative schemes involved gaseous LSD, bribing American mobster Sam Giancana (pictured) to carry out a hit, and poisoned ice cream.

© Getty Images

Project Iceworm -

One of the problems posed by early nuclear missiles was their limited range, which was an especially bothersome obstacle when your potential target was half a world away. One of the ways the US government, with the help of the CIA, tried to get around this issue was by building secret missile silos in the Arctic Circle, under the Greenland ice sheet.

© Getty Images

Project Iceworm -

For seven years, Denmark was completely unaware of the complex being built underneath their territory. The project was eventually called off in 1966, after shifts in the ice sheet rendered the plan unfeasible.

© Getty Images

Project Horizon -

In 1959, 10 years before NASA successfully put a man on the Moon, the US government drew up some extremely optimistic plans for a number of permanent lunar military bases, under the name Project Horizon.

© Public Domain

Project Horizon -

The outposts, which were projected to be operational by 1966, would have required 147 shuttles to transport all of the needed materials, and would be manned by 16 American soldiers. President Dwight D. Eisenhower quickly shut down the project once the burden of responsibility for space exploration was moved from internal agencies to NASA.

© Getty Images

The FBI’s warrantless surveillance -

A slightly less secretive agency of the United States government, the FBI came under widespread scrutiny in 2015 after an investigative report published by the Associated Press revealed they had been surveilling the general public from above.

© Getty Images

The FBI’s warrantless surveillance -

The report explained that the FBI had been using small aircraft registered to fake private companies all across the country to listen in on cell phone conversations and record video footage from above. Within one 30-day period, these surveillance planes had been spotted in 30 different US cities.

© Getty Images

The Bikini Atoll nuclear tests -

While the deserts of Arizona and New Mexico are usually what come to mind when one imagines nuclear test sites, one of the most heavily-bombed sites in US history was once a Pacific Island paradise.

© Getty Images

The Bikini Atoll nuclear tests -

Right after the end of World War II and the bombing of Hiroshima and Nagasaki, nuclear testing continued in full force on the Marshall Islands, specifically in the Bikini Atoll, where 23 nuclear bombs were detonated between 1946 and 1958. These islands weren’t uninhabited, with the government forcibly removed the nearly 200 residents who had called the islands their home.

© Getty Images

The 1968 B-52 crash -

In 1968, a B-52 bomber plane carrying four nuclear bombs was making routine rounds around Greenland’s Thule airport base when it unexpectedly crashed into the surrounding snowy wilderness. Authorities immediately went out to account for the plane's nuclear payloads, and announced a success shortly afterwards. It wasn’t until 2008 that the BBC reported on classified documents that revealed one of the bombs was never located.

Sources: (NPR) (Gerald R. Ford Presidential Library and Museum) (MIT Technology Review) (Associated Press)

See also: Military secrets the government doesn't want you to know

© Getty Images