text: Hoffman, 40, sunk nine birdies in a seven-under-par 65 to lead ahead of compatriot William McGirt.
  Lee Westwood is third on two under, one ahead of fellow Englishmen Justin Rose, Andy Sullivan and Matt Fitzpatrick.
  Northern Ireland's Rory McIlroy rallied with three late birdies in a 72, while 2015 champion Jordan Spieth carded 75.
  England's reigning champion Danny Willett started his defence with a double bogey and a bogey before fighting back to finish one-over par.
  World number one Dustin Johnson pulled out on the first tee after injuring his back when slipping on the stairs at his rental house on Wednesday.
  Scoring was expected to be tough at Augusta with high winds forecast to become even stronger as the opening day progressed.
  And that proved to be the case as it became a distinct possibility that no player would shoot under 70 in the opening round for the first time in 60 years.
  But the tricky conditions proved little obstacle for McGirt and, particularly, Hoffman, who were the only players to do so.
  Hoffman has only previously claimed one top-25 finish at a major, tying for ninth at the 2015 Masters, but put together a remarkable round.
  The world number 52 closed the front nine with two birdies to move two-under, then blitzed the back nine with a five-under 31 which included four straight birdies.
  The Californian almost made it five on the last, only to see a 16-foot putt fall agonisingly short.
  Nevertheless, his four-shot lead is the biggest first-round advantage at Augusta since 1941.
  "The putts started going in the hole - as simple as that sounds," he said.
  "I kept hitting my spots and in the wind I ended up getting 20 footers and I got some of them down the stretch."
  McGirt, making his Masters debut, became the first player to break 70 with four birdies and a bogey in a three-under 69.
  The 37-year-old from South Carolina does not have much previous pedigree in the majors, having missed the cut at the US Open and The Open in 2016 before earning a 10th place finish at last year's PGA Championship.
  "It was pretty darn special. Any time to break 70 is awesome," said McGirt, who is ranked a place below Hoffman at 53rd in the world.
  "The few times I came down here to play in practice the wind direction was the same so this was not new to me today.
  "I'm lucky enough to know a few members here and I've spoken to a few caddies and they've been happy to share their knowledge with me."
  Defending champion Willett headed a record 11 English players starting in the 93-strong field at Augusta, but made a nightmare start to his defence with a double bogey and a bogey in the opening two holes.
  Birdies on three and 10, with six successive pars sandwiched in-between, steadied the Yorkshireman's scorecard and a superb eagle on the par-five 13th moved him level par for the first time.
  However, a bogey on the 18th pushed him back over par.
  "Battling back from three over even if it was flat and calm round this place would have been great," said the world number 17, who has not won a tournament since claiming the Green Jacket.
  "We gathered ourselves after probably the worst start we could have wished for. A score of 73 seemed like a good score."
  On returning to the scene of his greatest triumph for the first time, he added: "The memories came flooding back. To be anywhere defending a title is incredible but to be here at Augusta National is amazing - at least once in your life, but it would be nice to do it a couple of times."
  Willett became the first Englishman to win the Masters in 20 years when he overhauled Spieth 12 months ago, and a number of his compatriots are in close contention as they aim to repeat his feat.
  Fitzpatrick, the 22-year-old from Sheffield, led for a short period at three-under before a double bogey on the 18th dropped him back into the pack also containing Sullivan and Rose.
  Westwood, 43, surged into third place with five straight birdies on the back half as he continues his search for a first major title.
  World number two McIlroy, 27, is aiming to become only the sixth man to win all four majors - at his third time of trying at Augusta.
  McIlroy is seeking a first Masters title following victories at the US Open, the Open Championship and the US PGA Championship.
  And, after three consecutive top-10 finishes, he has made no secret that finally winning the Green Jacket is his main priority.
  The Northern Irishman made a scruffy start to his opening round, however, dropping three shots without making a birdie on the front nine.
  Gutsy par putts on 10, 11 and 12 prevented him dropping further adrift, setting the platform to haul himself back to level par with three birdies in the final six holes.
  "After nine holes if someone had said I would shoot even par I would have ripped their hand off," he said.
  Two-time major winner Jordan Spieth is hoping to banish memories of last year's spectacular final-day collapse by winning his second Masters.
  The American, 23, led by five shots as he approached the 10th, only to dramatically drop six shots in three holes - including a quadruple bogey seven at the 12th - and allow England's Willett to take advantage.
  He was putting together an encouraging first round on Thursday until another quadruple bogey wrecked his card, although at three over par he is still in contention.
  Spieth was among the leaders heading into Amen Corner, coming through the tough trio of 11, 12 and 13 unscathed.
  He found the green on the iconic par-three 12th to huge cheers, then birdied the par-five 13th to move into a 13-man share of the lead at one under.
  "I was relieved to see it down and on the green," he said of his tee shot on 12. "And I guess everybody else felt maybe more than I did on it."
  But his opening-day challenge faded quickly as a bogey on the 14th was followed by a nine on the par-five 15th.
  Spieth's approach fizzed back off the green into the water and after taking a penalty drop, he knocked his fifth shot over the back, then hit a poor chip before needing three putts from 30 feet.
  "It was nice to make a three at 12 and then four at the next," he added. "I really thought we had it going there and just made a club choice mistake on 15 but we're still in the tournament."
  Belgium's Thomas Pieters - considered one of the rising stars on the European Tour - was one of the few players who managed to tame Augusta early on Thursday.
  He moved into an early four-shot lead on his Masters debut, rattling in five birdies in his opening 10 holes.
  Then, the 22-year-old came unstuck at Amen Corner.
  He signed for his first bogey at Augusta by three-putting on the 11th, but worse was soon to follow at the 12th.
  Pieters dunked his tee-shot into Rae's Creek - the water hazard guarding the narrow green - before knocking on and needing two putts for a double bogey.
  And another double bogey at the last dropped him back to level par alongside McIlroy, Ireland's Shane Lowry, England's Paul Casey and four-time major winner Ernie Els.
  Iain Carter, BBC golf correspondent at Augusta:
  "This was a day not to play yourself out of the Masters.
  "Today, you couldn't win the tournament but you could lose it.
  "All of the players that have battled to around par have kept themselves in it."
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target: Unheralded American Charley Hoffman defied tricky blustery conditions to take a four-shot lead after day one of the 2017 Masters at Augusta National.