The Basic Instinct star made the admission in his new memoir, titled One Helluva Ride, as he explained how he managed to rule himself out of fighting in the war - which he was also protesting at the time - by exaggerating the effects of a spinal condition he had recently been diagnosed with.
"When I went in for my physical, they found something called spondylitis, which in my case meant I was missing a portion of my vertebrae and there was a curvature of my spine," he wrote.
"This was good news - the doctor gave me a letter about my condition that I could show draft officers. The bad news was the letter had adjectives like 'mild' and 'slight.'"
Douglas then enlisted the help of his dad Kirk, who asked the doctor to write a new letter "without the qualifiers".
"The next time my lottery number was pulled, I wore a big white brace that belted from the front," he wrote.
"I showed him [the sergeant] the paper and he said, 'Take off that brace.' I said, 'I cannot, sir.' 'What do you mean?' he demanded. I told him I would fall if I did.
"They gave me a 1-Y designation, which meant I was only to be called if the nation was facing a dire emergency."
"I'm not proud of this story. I am just being honest," he wrote.
The Oscar-winning actor took on his first major role in the film Hail, Hero!, which was released in 1969, at the height of the Vietnam War.
He also reflected on protesting the war at the same time as his father was in the "middle of a five-year run as goodwill ambassador, touring the world to promote American exceptionalism".
"I was protesting a country he was celebrating. My father was ultimately a very patriotic guy, and I was at a college that was celebrating rebellion."
16°C