For eight years, Mark Kuhns and his 15-member team carried out a secret operation to restore the sanctity of golf at Oakmont Country Club.

The crew used the cover of darkness to topple white oaks, blue spruce, and cherry trees that graced the western Pennsylvania golf course and feed them into wood-chipping machines.

Oakmont, site of this week’s U.S. Open, has cut down about 5,000 trees since the early 1990s to remove nature’s wind barriers and subject players to more daunting conditions. While the mission initially angered members, it eventually restored the 103-year-old course to the way Pittsburgh entrepreneur Henry C. Fownes designed it.

“It was a very secretive program,” said Kuhns, the course’s greenskeeper from 1991 to 1999. “It’s a very sensitive issue removing trees anywhere, but you’re either going to play golf or you’re going to admire the trees.”

From the moment local favorite Arnold Palmer lost to long- hitting Jack Nicklaus in a playoff at the 1962 U.S. Open at Oakmont, club members began looking for ways to keep their course from being made obsolete by power. Trees were the answer, the members decided. So they planted thousands of them, which narrowed the fairways and penalized wayward shots.

“Jack really put a lot of fear in the membership here,” said Rob Hoffman, a former club president.

Thirty years on, the course had become choked by roots and overhanging branches, blocking sunlight on tees and greens. Wind no longer was a feared playing element. Worst of all, trees made the course easier by framing the holes, Kuhns said.

“We knew we had a problem,” said Kuhns, who is now greenskeeper at Baltusrol Golf Club in Springfield, New Jersey.

Kuhns was ordered by then-club chairman Jim Malone to remove trees without angering members. Night afforded the best protection.

Kuhns’s crew could get rid of a tree in an hour without leaving any sign that it was ever there. Tarps were spread on the ground to collect sawdust.

“We removed the tree, removed the limbs, removed the stump and grounded it out,” he said. “We had the earth ready to fill in the hole, had it all cut out for sod and had it sodded within an hour.”

Workers would do four or five a night. When checking a sodded area one morning, a member questioned Kuhns, who said he became known as the “Butcher of Oakmont” by club members.

“He came up behind me and said, ‘Oh, what happened here?”‘ Kuhns recalled. “He saw there was fresh sod. And I said, ‘Oh, terrible irrigation break last night.”‘

The member told Kuhns he did “a nice job of fixing it up,” but never realized the tree was gone.

The club eventually found that removing the trees exposed the course to more sunlight, allowing for longer, thicker rough that also put a premium on accurate shots.

After about 1,000 trees were removed, the operation was exposed. Members were told that the plan was to return the course to its original design, and dissension subsided.