"At the heart of every legend is a grain of truth," is a great quote to sum up these five conspiracy theories that most people believed were false, but actually turned out to be quite true.

Of course, as with most conspiracy theories, they seem far-fetched and implausible until further evidence comes along and either debunks or confirms much of what’s been said.

Here are five conspiracy theories that everyone thought were utterly insane until that grain of truth was finally found:

1) The United States Navy attacked Vietnamese torpedo boats that never really existed

It was reported that on the evening of August 4th, 1965, the USS Maddoxbegan to engage in naval combat with North Vietnamese torpedo boats shortly after being attacked without provocation. Lyndon Johnson, who was president at the time, even went so far as to say thatthey sunk two Vietnamese ships.

But, after some NSA documents were declassified, it came out that the whole event was staged in order to justify further involvement in the Vietnam conflict.

"I had the best seat in the house to watch that event, and our destroyers were just shooting at phantom targets — there were no PT boats there… There was nothing there but black water and American fire power," said one Navy pilotand Medal of Honor recipient.

2) The FBI elaborately tried to suppress American political movements they deemed "subversive"

Under director J. Edgar Hoover, the Federal Bureau of Investigation conducted a secret program, called COINTELPRO (counter-intelligence program), designed specifically to harass and dissuadethe members of certain political movements.

Author of "The United States of Paranoia," Jesse Walker, says:

"Under COINTELPRO, FBI agents infiltrated political groups and spread rumors that loyal members were the real infiltrators. They tried to get targets fired from their jobs, and they tried to break up the targets’ marriages. They published deliberately inflammatory literature in the names of the organizations they wanted to discredit, and they drove wedges between groups that might otherwise be allied. In Baltimore, the FBI’s operatives in the Black Panther Party were instructed to denounce Students for a Democratic Society as "a cowardly, honky group" who wanted to exploit the Panthers by giving them all the violent, dangerous "dirty work." The operation was apparently successful: In August 1969, just five months after the initial instructions went out, the Baltimore FBI reported that the local Panther branch had ordered its members not to associate with SDS members or attend any SDS events."

This theory was proved true after a group of anti-war activists broke into an FBI field office where they found a huge stash of documents proving that the program existed.

3) U.S. Military officials were going to kill innocent people and blame it on Cuba

If you can remember back to the Cold War era, one of the biggest Communist threats to America at the time was our neighbor, Cuba.

They tried to rid Cuba of its leader, Fidel Castro, in 1961, but failed. So, they came up with another idea called ‘Operation Northwoods.’

All of the Joint Chiefs of Staff approvedof ‘embarrassing plans’ to kill innocent people in order to paint the picture of a dangerous, irresponsible Cuban nation. These plans included firing mortar rounds into the United States Guantanamo naval base, blowing up aircraft and ammunition supplies, and even blowing up an entire ship in the harbor.

The most extreme operation they had plannedwas to implement a scare-tactic campaign in Miami. This would involve sinking a boat full of Cubans on their way to Florida with carefully planned explosions, as well as the arrest of Cuban agents, and documents detailing Cuban involvement.

4) The CIA hired prominent American journalists to disseminate propaganda through the media and gather information

In the 1950s during the Cold War, the Central Intelligence Agency of the United States used American journalists to sway public opinion and gather information in an operation called ‘Operation Mockingbird.’ This operation would be in effect for over three decades.

Journalist Carl Bernstein explains the operation for Rolling Stone back in 1977:

"Some of these journalists’ relationships with the Agency were tacit; some were explicit. There was cooperation, accommodation and overlap. Journalists provided a full range of clandestine services — from simple intelligence-gathering to serving as go‑betweens with spies in Communist countries. Reporters shared their notebooks with the CIA. Editors shared their staffs. Some of the journalists were Pulitzer Prize winners, distinguished reporters who considered themselves ambassadors without‑portfolio for their country. Most were less exalted: foreign correspondents who found that their association with the Agency helped their work; stringers and freelancers who were as interested in the derring‑do of the spy business as in filing articles; and, the smallest category, full‑time CIA employees masquerading as journalists abroad. In many instances, CIA documents show, journalists were engaged to perform tasks for the CIA with the consent of the managements of America’s leading news organizations."

This long-standing program was revealed by the Church Committee in a full report stating that the "CIA currently maintains a network of several hundred foreign individuals around the world who provide intelligence for the CIA and at times attempt to influence opinion through the use of covert propaganda. These individuals provide the CIA with direct access to a large number of newspapers and periodicals, scores of press services and news agencies, radio and television stations, commercial book publishers, and other foreign media outlets."

5) The CIA performed ‘mind control’ experiments on unknowing US and Canadian citizens

One of the craziest theories to have been confirmed is the CIA program notoriously known as MKUltra. This program’s purpose was to develop a further understanding of biological and chemical weaponry during the Cold War. Eventually,the program grewto include much more, however.

Research expanded into areas like: promoting the intoxicating effect of alcohol, how to increase usefulness of hypnosis, how to make a person more resistant to privation, torture and coercion during interrogation or brain-washing, how to induce amnesia, how to produce shock and confusion for long periods of time, and how to manifest physical disablement in humans via paralysis of the legs, acute anemia, and other methods.

Operating under front companies, the CIA worked with over 80 different institutions to run experiments on different human subjects. The Church Committee attributes at least two deaths of American citizens to the program. These top secret files revealed by the Church Committee were destroyed by CIA Director Richard Helms in 1973.

Bonus (Theory)! Hitler didn’t die in Germany, he died in Argentina

While this has yet to be proven, one of the most prominent conspiracy theories floating around today is the one that tells us that Hitler did not take his own life in Berlin in 1945, but rather he escaped to Argentina where he lived for another 17 years.

British journalist Gerrard Williams makes a compelling case in his new book that "Hitler died an old man in South America." The book tells us that Hitler raised two daughters in Argentina before passing away in 1962. Additionally, they claim that the skull fragment believed to be from Hitler’s gunshot wound to the head is actually from a young woman.

"Stalin, Eisenhower and Hoover of the FBI all knew there was no proof of him dying in the bunker," Williams tells us.