On Dec. 15, 1982, New York Giants defensive coordinator/linebackers coach Bill Parcells was promoted to head coach.

George Young, the Giants’ astute general manager, picked the right guy to rebuild the moribund NFL franchise. The Giants, who had had two winning seasons in the previous decade, were coming off a 4-5 campaign in the strike-shortened 1982 season under Ray Perkins, who had played under the legendary Paul “Bear” Bryant at the University of Alabama.

In 1981, Perkins, a former NFL receiver, led the Giants (9-7) to their first playoff berth since 1963. But Bryant’s retirement after the 1982 season set in motion a string of events.

For Parcells, the 1983 season represented his first head coaching opportunity at the pro level. The New Jersey native had one full season as a college head coach on his résumé up to that point, finishing 3-8 at Air Force in 1978.

After four seasons as an NFL assistant coach (three with the Giants, 1979, 1981-82 and one with the New England Patriots in between those two stints), he was 41 years old and ready for a fresh start. More responsibility. More scrutiny. More money.

“Continuity is important, but you want to get the best guy,” Young was quoted as saying by The New York Times, explaining his decision to appoint Parcells as the team’s next head coach. “If he contributes to the continuity, fine, but you want to get the best guy. You don’t get the continuity guy first; you get the best guy first.”

Young insisted he got the best guy.

“Bill Parcells was first on my list, and it was a short list,” the GM said, according to The Times.

What happened in the 1983 season?

The Giants were awful, finishing with a 3-12-1 record.

But in Parcells’ second season at the helm, they went 9-7.

In 1986, they went 14-2, tying the defending champion Chicago Bears for the best regular-season record en route to the franchise’s first Super Bowl triumph in January 1987.

Parcells let the Giants to their second Super Bowl title after the 1990 season.

Then he retired from coaching before resurfacing as a reclamation project wizard with the New England Patriots (1993-96; the Pats fell to the Green Bay Packers in his final season with the club), the New York Jets (1997-99; after a 1-15 season in ’96, Parcells guided the Jets’ improbable turnaround the next year — eight more wins — and a trip to the AFC Championship Game in’98) and the Dallas Cowboys (2003-06, a five-win improvement from 2002 to Parcells’ first season in Big D).

Beyond Parcells’ three trips to the Super Bowl and 10 playoff berths in 19 seasons with the aforementioned four teams, working for the future Pro Football Hall of Fame inductee became a career boon for dozens of men.

Consider: The Parcells coaching tree, most notably ex-Giants defensive coordinator Bill Belichick (the Patriots boss since 2000 and, for coaches, a winner of a record six Super Bowls), has been firmly entrenched in the NFL for decades.

In addition to Belichick, former Parcells assistants Tom Coughlin and Sean Payton won Super Bowls as head coaches of the Giants and New Orleans Saints, respectively. Coughlin holds bragging rights over Payton, winning two titles to his one.

All told, 17 ex-Parcells assistants have served as NFL or NCAA college football head coaches. And 10 became NFL GMs.

George Young made the right call in December 1982. Ten days before Christmas, he offered Bill Parcells the job he was born to do.

And the rest is history.