Take off your tin-foil hats for a second, because sometimes an insane-sounding conspiracy theory actually turns out to be true.

From the government making up an enemy attack to justify war to “mind control” experiments, some stories are hard to believe until declassified documents or investigations prove they actually happened.

Here are five of the wildest former conspiracy theories we found:

1. The US Navy fired on North Vietnamese torpedo boats that weren’t even there.

On the night of Aug. 4, 1965, the USS Maddox engaged against hostile North Vietnamese torpedo boats following an unprovoked attack. The only problem: there were no torpedo boats. Or an attack.

The Maddox fired at nothing, but the incident was used as a justification to further escalate the conflict in Vietnam.

US Marines landing in Vietnam US Marine Corps President Lyndon Johnson reported that at least two of the enemy boats were sunk, and American media outlets backed up that story in numerous articles. But conspiracy theorists thought it looked a lot like a “false flag” attack. They were right, according to the National Security Agency’s own declassified documents.

Others who were present, including James Stockdale — a Navy pilot who would later receive the Medal of Honor — disputed the official account:

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.

Even LBJ wasn’t convinced: “For all I know, our Navy was shooting at whales out there.”

2. The FBI infiltrated, surveilled, and tried to discredit American political groups it deemed “subversive.”

When it wasn’t investigating crimes, the Federal Bureau of Investigation under Director J. Edgar Hoover kept busy trying to suppress the spread of communism in the Unites States. Under a secret program called COINTELPRO (counter-intelligence program), the FBI harassed numerous political groups and turned many of its members completely paranoid.

J. Edgar Hoover in 1971 AP Though they could never be sure, many activists suspected the FBI was watching them. And the Bureau was able to mess with groups it didn’t like and influence what they did.

From the book “The United States of Paranoia” by Jesse Walker:

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.

It wasn’t only communist or left-leaning organizations. The FBI’s list of targets included the Civil Rights movement, and public enemy number one was Dr. Martin Luther King. Agents bugged his hotel rooms, followed him, tried to break up his marriage, and at one point even sent him an anonymous letter trying to get him to commit suicide.

It would’ve been just a whacky conspiracy theory from a bunch of paranoid leftists that no one would’ve believed. But the conspiracy theorists — a group of eight anti-war activists — broke into an FBI field office in 1971 and found a trove of documents that exposed the program.

3. US military leaders had a plan to kill innocent people and blame it all on Cuba.

Sitting just 90 miles from the Florida coast and considered a serious threat during Cold War, communist Cuba under its leader Fidel Castro was a problem for the United States. The US tried to oust Castro during the Bay of Pigs invasion of 1961, but the operation failed. So the generals went back to the drawing board and came up with an unbelievable plan called Operation Northwoods.

Fidel Castro Wikimedia Commons

From ABC News:

The plans had the written approval of all of the Joint Chiefs of Staff and were presented to President Kennedy’s defense secretary, Robert McNamara, in March 1962. But they apparently were rejected by the civilian leadership and have gone undisclosed for nearly 40 years.

“These were Joint Chiefs of Staff documents. The reason these were held secret for so long is the Joint Chiefs never wanted to give these up because they were so embarrassing,” Bamford told ABCNEWS.com.

What were the “embarrassing” plans? There were ideas for lobbing mortars into Guantanamo naval base, in addition to blowing up some of the aircraft or ammunition there. Then there was another idea floated to blow up a ship in its harbor. But these were timid compared to other plans that came later in a top secret paper:

We could develop a Communist Cuba terror campaign in the Miami area, in other Florida cities and even in Washington … We could sink a boatload of Cubans enroute to Florida (real or simulated) … Exploding a few plastic bombs in carefully chosen spots, the arrest of Cuban agents and the release of prepared documents substantiating Cuban involvement also would be helpful in projecting the idea of an irresponsible government.

The paper went on to describe in detail other plans for possibly hijacking or shooting down a “drone” airliner made to look like it was carrying civilian passengers, or faking a shoot-down of a US Air Force jet over international waters to blame Cuba.

4. The CIA recruited top American journalists to spread propaganda in the media and gather intelligence.

Started in the 1950s amid the backdrop of the Cold War, the Central Intelligence Agency approached leading American journalists in an attempt to influence public opinion and gather intelligence. The program, called Operation Mockingbird, went on for nearly three decades.

From journalist Carl Bernstein, writing in Rolling Stone 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.

The Church Committee exposed much of the program, with a full report from Congress stating: “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 conducted “mind control” experiments on unwitting US and Canadian citizens, some of which were lethal.

Perhaps one of the most shocking conspiracy theories that turned out to be true was a CIA program called MKUltra, which had the stated goal of developing biological and chemical weapons capability during the Cold War, according to Gizmodo. But it ballooned into a larger program that encompassed research (via Today I Found Out):

which will promote the intoxicating affect of alcohol;

which will render the induction of hypnosis easier or otherwise enhance its usefulness;

which will enhance the ability of individuals to withstand privation, torture and coercion during interrogation and so called “brain-washing;”

which will produce amnesia for events preceding and during their use;

[which will produce] shock and confusion over extended periods of time and capable of surreptitious use; and

which will produce physical disablement such as paralysis of the legs, acute anemia, etc.

During the program, the CIA established front companies to work with more than 80 institutions, such as hospitals, prisons, and universities. With these partnerships in place, the agency then ran experiments on subjects using drugs, hypnosis, and verbal and physical abuse. At least two American deaths can be attributed to this program, according to the Church Committee.

Though the Church Committee uncovered much of this shocking program, many of the top secret files were ordered destroyed in 1973 by CIA Director Richard Helms.