TOM Brokaw shocked his Anchor-desk cronies, Peter Jennings and Dan Rather, when he first announced his retirement from “NBC Nightly News.”

The move marked the beginning of the end for the decades-long dominance of the three evening news anchors and the rise of cable news.

“It’s fair to say that they were both a little surprised that I made this decision,” Brokaw, 64, told The Post about the fallout of his choice two years ago to hand off the anchor desk to Brian Williams.

Brokaw’s final telecast as the anchor of “Nightly News” will be tonight and will be only slightly different from a thousand others that he’s done, he says.

“I’m hoping to go off the air on a graceful note, I’m going to say something at the end to the audience,” he says, adding that his wife, Meredith – they’ve been married since 1962 – might come in to work with him for the first time in his 22 years behind the anchor desk.

“I often say that I’m always pleased when she remembers what I do for a living,” he jokes. “It has not defined our lives absolutely – it’s obviously been a great privilege, but we have other parts of our life.”

Leaving the broadcast, he says, “was something that I had been thinking about for a long time, and they [NBC News] wanted to make sure that the viewers knew that we had a transition in mind, and they wanted to give Brian the assurance that he had the job so that he wouldn’t be picked off by one of the other networks.”

The decision has spared NBC the agony of speculation that’s dogging CBS News now, following Rather’s sudden plans to depart from “CBS Evening News” in a few months without naming an heir apparent.

Brokaw says the fuss and media blitz leading up to his final broadcast tonight has left him red-faced.

“I am a little bit embarrassed,” he says. “It seems like an out-of-body experience. I’ve spent most of my career putting my head down and doing as much work as I can and then to get all of this attention is a little overwhelming.”

His greatest regret was not covering international terrorism as thoroughly as he possibly could have before 9/11.

“I wish that we had done a better job in dealing with terrorism at an earlier stage,” he says. “There were signs aplenty out there, attacks on embassies, the [warship] U.S.S. Cole, the Khobar Towers [in Saudi Arabia] – all those things. But we didn’t connect the dots the way we should have.”

Brokaw says his most difficult time on the air was during 9/11 and right afterwards.

“I think this holds true to Dan and Peter as well,” he says.

“At the end of whatever that period was, however many days it took before we could move on to the new reality, I think that all three of us felt that we had done the very best that we could,” he says. “I have often said that those are the stories for which they invent anchormen and those are times that we really earn our keep.”