He is best known for his time in New Japan Pro-Wrestling (NJPW), where he was a former three-time IWGP Tag Team Champion as part of the Killer Elite Squad with Lance Archer, as well as being a two-time GHC Tag Team Champion in Pro Wrestling Noah (also alongside Archer) due to NJPW's working relationship with Pro Wrestling Noah.

He is of predominantly British descent through his father, professional wrestler David Smith who was from Greater Manchester, England, and his mother Diana Hart who belongs to a large family of Ulster Scot heritage.

[27] He made an early appearance with the then World Wrestling Federation (now WWE) on October 5, 1996, at the age of 11 when he teamed with his cousin Ted Annis against TJ Wilson and Andrew Picarnia at a WWF house show in Calgary.

[30] Smith was billed as the mystery opponent of NWA World Heavyweight Champion Jeff Jarrett, ostensibly hand-picked by his uncle, Bret Hart.

He returned to Stampede Wrestling in October 2005, and on November 25, 2005, was defeated by T.J. Wilson in the finals of a tournament for the vacant North American Heavyweight Championship.

[29] While there, Smith met with WWE executives, John Laurinaitis and Carl De Marco, and signed a developmental contract with on April 4, 2006.

[1][29][31] He wrestled dark matches for the company before his debut, defeating wrestlers like Rob Conway and Mike Knox, and losing to Randy Orton.

[32][33] Harry debuted in Ohio Valley Wrestling (OVW), at the February 14, 2007 television tapings, in a tag team match with Kofi Nahaje Kingston, in which they defeated The Belgium Brawler and Nicholas Sinn.

[44] He made his television debut as "DH Smith" on the October 22, 2007 episode of Raw, defeating Carlito using his father's trademark running powerslam.

After losing to Kidd, Smith would be restricted to appearing on Superstars, mostly participating in tag team matches with Yoshi Tatsu or Darren Young.

On August 20, 2011, Smith, working under his real name, made his return to the independent circuit defeating Dan Maff at Pro Wrestling Syndicate.

[83] On August 27, 2011, Smith, working under his real name, made his debut for Japanese Inoki Genome Federation (IGF), losing to Hideki Suzuki.

[87] On January 20, Smith teamed up with Chavo, Jwala, Mahabali Veera and Matt Morgan to take on Abyss, Deadly Danda, Scott Steiner, Sir Brutus Magnus and Sonjay Dutt in World Cup Of Ring Ka King steel cage match and won.

[91] On June 28, 2024, Smith challenged Innovative Hybrid Wrestling Champion "The King" JP Simms for the IHW Championship at the Riverview Sunfest.

On August 13, 2012, New Japan Pro-Wrestling announced that Smith would be returning to the promotion the following month as a member of Minoru Suzuki's Suzuki-gun stable, forming a regular tag team with stablemate Lance Archer.

took part in the round-robin portion of the 2012 World Tag League, finishing with a record of four wins and two losses, advancing to the semifinals of the tournament in the second place in their group.

[110] On April 5, Smith and Archer made their fourth successful defense of the IWGP Tag Team Championship against Shinsuke Nakamura and Tomohiro Ishii.

lost the IWGP Tag Team Championship back to Tencozy in a four-way match, which also included Takashi Iizuka and Toru Yano, and Manabu Nakanishi and Strong Man, though neither Smith nor Archer was involved in the finish.

failed to regain the NWA World Tag Team Championship from Tencozy in a three-way match, which also included Rob Conway and Wes Brisco.

unsuccessfully challenged Ishii and Yano for the IWGP Tag Team Championship in a three-way match, also involving Togi Makabe and Tomoaki Honma.

were primed for a run as NJPW's top foreign tag team, but the plan was changed when Archer was forced to undergo surgery on a herniated disc in his back.

took part in the 2017 World Tag League, where they finished with a record of five wins and two losses, failing to advance to the finals due to losing to block winners Guerrillas of Destiny in their head-to-head match.

He lost against Toru Yano in the first round of the 2018 New Japan Cup[155] and faced the IWGP Tag Team Champions Los Ingobernables de Japón at Wrestling Honokuni.

On the November 2, edition of Fusion the Hart Foundation beat ACH, Swann and Marko Stunt in a six-man tag team match.

On March 12, during the After the Bell podcast hosted by Corey Graves, it was announced that Smith's father, The British Bulldog, would be going into the 2020 Hall of Fame class, but the event was postponed to the following year due to the COVID-19 pandemic.

On June 11, Smith & Doug Williams, now called the Commonwealth Connection defeated La Rebelión to win the NWA World Tag Team Championship.

[172] On February 29, 2024 at Intimidation Games, Smith and Tom Lawlor defeated The Second Gear Crew (Matthew Justice and 1 Called Manders) to win the MLW World Tag Team Championship.

[14] He originally intended to pursue a career in MMA after being released from WWE in 2011 and trained at Dave Batista's Gracie Fighter Tampa school.

[179] In August 2016, he won the expert level super heavyweight division at NAGA in Las Vegas, coached by Barnett and Erik Paulson.

[187][188] On April 7, 2018, at a WrestleCon event in New Orleans, Louisiana, Smith threw a cup of coffee at Jake "The Snake" Roberts' face during a verbal argument before fleeing the scene.