Dr. Sanjay Gupta, a practicing neurosurgeon, is the multiple Emmy-award winning chief medical correspondent for CNN. The views expressed are his own.

(CNN) When the U.S. military launched Operation Golden Flow nearly 45 years ago, no one could have anticipated the impact it would have on the study of addiction, behavior and your brain.

It was 1971 and U.S. Reps. Robert Steele and Morgan Murphy had just returned from an official visit to Vietnam with news that stunned the American public: 15% of the active soldiers were heroin addicts. Given President Richard Nixon's promises to both end the war in Vietnam and solve the rising domestic crime rate, this news was especially unsettling.

As a result, Operation Golden Flow was born.

It is what it sounds like. American soldiers in Vietnam would not be permitted to board a plane home until they passed a urine drug test. If they failed, the soldiers would be forced to stay in Vietnam, detox and try again. The expectations were low, given the extraordinary addictiveness of heroin. It was already thought to be the most addictive substance ever produced and impossible to escape.

Why is heroin so addictive?

Researchers at Johns Hopkins were wondering the same thing, right around the same time. In 1972, they stumbled onto an unexpected explanation. They discovered the brains of humans contained naturally occurring receptors for opium. The implications of this were significant. It meant substances such as codeine, morphine and heroin had a natural landing spot in the brain. When ingested, they would light up something primitive deep in our neurons. This is a trait all humans share, evolutionarily.

Even more remarkably, they figured out the active ingredients in opium, and all of its derivatives, were nearly identical to chemicals we already have in our brains -- endorphins -- the feel-good stuff giving us a sense of euphoria after we exercise. (They finally had proof a runner's high really was a runner's high!)

As a result of their work, we now know endorphins are the natural opiates of the human body. And, like opium, not only did endorphins relieve pain, they made us feel good. Really good. Sometimes addictively good.

The problem is, unlike endorphins, opium doesn't require us to exercise to get that good feeling. We could now simply get it through an injection.

Photos: 2016 candidates respond to NH heroin crisis Photos: 2016 candidates respond to NH heroin crisis Hide Caption 1 of 12 Photos: 2016 candidates respond to NH heroin crisis Hide Caption 2 of 12 Photos: 2016 candidates respond to NH heroin crisis Hide Caption 3 of 12 Photos: 2016 candidates respond to NH heroin crisis Hide Caption 4 of 12 Photos: 2016 candidates respond to NH heroin crisis Hide Caption 5 of 12 Photos: 2016 candidates respond to NH heroin crisis Hide Caption 6 of 12 Photos: 2016 candidates respond to NH heroin crisis Hide Caption 7 of 12 Photos: 2016 candidates respond to NH heroin crisis Hide Caption 8 of 12 Photos: 2016 candidates respond to NH heroin crisis Hide Caption 9 of 12 Photos: 2016 candidates respond to NH heroin crisis Hide Caption 10 of 12 Photos: 2016 candidates respond to NH heroin crisis Hide Caption 11 of 12 Photos: 2016 candidates respond to NH heroin crisis Hide Caption 12 of 12

And none of the opiates worked faster than heroin. Its chemical structure allowed it to be soluble in fat, and cross the blood brain barrier resulting in a near immediate rush, and subsequent high.

It was almost as if it was chemically designed to be addictive, which of course it was.

To make matters worse, frequent users of heroin slowly dampen their brain's feel-good reward centers, known as the nucleus accumbens, which is stimulated by dopamine. When someone takes a substance like heroin, as opposed to relying on natural endorphins, the dopamine surge is more rapid and longer lasting. The problem is the nucleus accumbens can start to become fatigued from such excessive stimulation. The result: An addict needs escalating doses of heroin to get increasingly diminished pleasure.

In addition, a heroin user would now have a reward center in the brain with very low levels of baseline activity. So when they weren't using heroin, they crashed and hard -- which helped explain the dramatic highs and lows of the heroin addicts brain.

For all these reasons, heroin became scientifically regarded as one of the most dangerously addictive drugs on the planet, in terms of dependence, withdrawal, tolerance, reinforcement and intoxication. Relapse is almost guaranteed, and heroin use is now intensifying dramatically, even in previously unexpected populations. Some of the greatest increases are occurring in higher income women and overdose deaths from opiates have quadrupled over the past 10 years, according to the Centers for Disease Control

Addiction and your environment

Back in 1971, during Operation Golden Flow, it was becoming increasingly clear addiction was a brain disease and that an individual's biology, along with the genes he or she was born with, accounted for about half of their addiction vulnerability. But the other half was more complicated, a product of their environment and its interplay with genetics.

This is where Operation Gold Rush would provide some startling insights. One thing was clear: The soldiers returning from Vietnam were about to undergo a dramatic transformation in their environment.

In Vietnam, not only was the location and culture wildly different than what the soldiers would experience back in the United States, they would also no longer endure the psychological whiplash of stagnant boredom and atrocious horror characterizing a battlefield. They would be reimmersed in a more mundane civilian life. That fact alone would tremendously impact their success in overcoming addiction.

Photos: Photos: Now going on eight years clean, Anthony Sideri volunteers at the local soup kitchen and speaks to high school students to encourage them not to fall down the path he took. Hide Caption 1 of 7 Photos: Sideri first started using alcohol and marijuana in high school, "thinking I was in total control of my life and my future." Hide Caption 2 of 7 Photos: After high school, he moved on to narcotic painkillers. When that no longer did the trick, he turned to heroin. Hide Caption 3 of 7 Photos: At 23, Sideri was snorting heroin every day, feeling "like I had it hidden from everybody." Hide Caption 4 of 7 Photos: On July 22, 2007, Sideri and a fellow addict robbed a bank to fuel their highs. These are the mugshots from his arrest. He spent a year in court-ordered rehab and 22 months in jail. Hide Caption 5 of 7 Photos: After his release, Sideri found happiness again. He married Jenna Buco, "the girl of his dreams," in 2011. Hide Caption 6 of 7 Photos: Sideri has a daughter and is attending school to become a substance abuse counselor. "It is so important for my daughter to see how I turned my life around." Hide Caption 7 of 7

Astonishingly, only 5% of the men who returned home after becoming addicted in Vietnam relapsed within a year. Just 12% relapsed, even briefly, within three years. It was astonishing because, on average, 78% of those admitted for heroin use had been in treatment at least once before, according to the Department of Health and Human Services.

There had never been a recovery program in history leading to the sort of success seen during Operation Gold Rush. For many, disrupting the environment of an addict would become standard in their approach to treatment.

Thanks to the work of psychologists, such as David Neal and Wendy Wood, we know even more about how our environment affects anyone's behavior . Walking by a smoking lounge can be torture for a smoker trying to quit, just like strolling by a bar can overwhelm a former alcoholic. The environment alone can be a powerful mental cue, which is irresistible.

Perhaps, like me, watching television cues you to eat a bowl of popcorn or ice cream. I don't need the ice cream by any means, and didn't even think about it a few minutes earlier, but the combination of environmental factors led me to the freezer.

Like the soldiers in Vietnam, though, disrupting our own environment can also result in enormous change. It is not that we need to experience war zones and then return home, but it may be changing around the furniture in a room where you are likely to have a drink. As Neal described, if you are going to continue to eat ice cream, try using your left hand if you are right handed , or perhaps eat it only while standing up. Slowly these environmental changes may cause you to break the behavioral cue and take a closer look at that cigarette, alcoholic drink and ice cream and fully realize you don't need it.

Operation Golden Rush helped make clear how this simple concept helped break the heroin addictions of Vietnam. It might help all of us in our daily lives as well.