Sumo's longest-serving yokozuna Hakuho retired on Thursday when the Japan Sumo Association's board of directors accepted his request to end a 20-year competitive career in Japan's ancient sport.

The Mongolian-born grand champion, winner of a record 45 grand sumo tournaments, has been dogged by injury the past few years and had surgery on his right knee in March. For the time being, he will serve as an instructor with his Miyagino stable as sumo elder Magaki.

Photo taken July 16, 2021, shows grand champion Hakuho performing a ring-entering ritual during the Nagoya Grand Sumo Tournament. The 36-year-old Mongolian-born yokozuna, winner of a record 45 titles, informed the Japan Sumo Association on Sept. 27 of his decision to retire. (Kyodo) ==Kyodo

The 36-year-old has been ranked as yokozuna for 84 tournaments, or about 14 years. His 45 titles in the top makuuchi division are more than anyone else in history.

Hakuho, who needed a good result in July after being reprimanded in November for missing bouts and tournaments due to injury and illness, bounced back from surgery to win all 15 of his bouts in the Nagoya tourney, capturing his final Emperor's Cup.

Yet despite the triumph, a source with knowledge of the matter said the yokozuna was not satisfied that his knee had recovered. Hakuho was forced to sit out September's tournament, which ended Sunday, due to multiple coronavirus cases in his stable.

By acquiring Japanese citizenship in September 2019, Hakuho became eligible to run his own stable of wrestlers after retirement.

With 1,187 career wins and 1,093 makuuchi division victories, Hakuho's career was filled with records and defining moments.

Sumo's 69th yokozuna, Hakuho, whose birth name is Monkhbatyn Davaajargal, debuted in the spring of 2001 and won his first top-division title at the summer meet in May 2006, when he first fought at the second-highest rank of ozeki.

Born in Ulaanbaatar, he was immersed in the Mongolian wrestling tradition from childhood. His father, Jigjidiin Monkhbat, competed in freestyle wrestling for Mongolia and won a silver medal at the 1968 Mexico City Olympics.

Standing 1.92 meters tall and weighing 155 kilograms, Hakuho was known for his wide-ranging attacking style and reached the highest rank of yokozuna ahead of the Nagoya meet in July 2007, aged 22 years and two months.

His fierce rivalry with fellow Mongolian-born grand champion Asashoryu captivated sumo fans until the latter's retirement in February 2010 left Hakuho as the only active yokozuna and the dominant force in the sport.

He won 63 consecutive bouts through November 2010, equaling the sport's second-longest winning streak. In January 2011, he became only the third wrestler to win six consecutive grand tournaments after former yokozuna Taiho and Asashoryu.

He claimed the all-time championship record with his 33rd career Emperor's Cup in January 2015, breaking the previous mark set by Taiho.

"He was always a huge wall," said elder Takekuma, the former ozeki Goeido. "I'm glad I was a contemporary of such a strong yokozuna and was able to compete against him."

Despite his outstanding contributions inside the dohyo, Hakuho at times earned the rebuke of sumo authorities for not adhering to the sport's strict protocols.

A day after capturing his 33rd championship, the judges ordered a rematch prompting some harsh word from Hakuho, who believed he clearly won, which did not sit well with the JSA.

After winning the March 2019 tournament, the last during Japan's Heisei era, he led the audience in an impromptu "tejime" clapping ceremony to mark the end of the era -- a stunt that brought down the house but disrupted the regimented post-tournament rituals, prompting a rebuke from the JSA and subsequent apology from the wrestler and his stablemaster.