Prisoner of war Jeremiah Denton declared his loyalty to the U.S. government during a 1966 interview for what was supposed to be a propaganda film. But his enraged captors missed his more covert message: “T-O-R-T-U-R-E,” blinked into the camera in Morse code, a dispatch that would alert the U.S. military to the conditions he endured.

Denton, who would survive 7 1/2 years confined in a tiny, stinking, windowless cell at the infamous “Hanoi Hilton” and other camps before his release in 1973, died of heart problems Friday in Virginia Beach, Va., at age 89, his grandson Edward Denton said.

Denton later became the first Republican from Alabama elected to the U.S. Senate since Reconstruction, although the iron will that allowed him to persevere in captivity gave rise to criticism he was too rigid a politician.

In July 1965, a month after he began flying combat missions for the Navy in Vietnam, the Mobile native was shot down near Thanh Hoa. He was captured and recalled his captivity in a book titled “When Hell Was in Session.”

“They beat you with fists and fan belts,” he told the Los Angeles Times in 1979. “They warmed you up and threatened you with death. Then they really got serious and gave you something called the rope trick.” The use of ropes – to cut off circulation in his limbs – left him with no feeling in his fingertips and intense muscle spasms, he said.

Some of the most severe torture came after the 1966 interview, in which he confounded his captors by saying that he continued to fully support the U.S. government, “and I will support it as long as I live.”

“In the early morning hours, I prayed that I could keep my sanity until they released me. I couldn’t even give in to their demands, because there were none. It was pure revenge,” Denton wrote.

The tape was widely seen, and U.S. intelligence experts had picked up the Morse Code message. But Denton theorized later that his captors likely figured it out only after he was awarded the Navy Cross – the second-highest decoration for valor – for the blinks in 1974.

With the war’s end drawing closer, he was released in February 1973.

Denton was the senior officer among former POWs who stepped off a plane at Clark Air Base in the Philippines. Denton spoke for the returning troops: “We are honored to have had the opportunity to serve our country under difficult circumstances. We are profoundly grateful to our commander-in-chief and to our nation for this day. God bless America.”