The National Olympic Committee of Ukraine said he had joined the armed forces in the early days of the war
King, along with Americans Rosemary Casals, Nancy Richey, Peaches Bartkowicz, Kristy Pigeon, Valerie Ziegenfuss, and Julie Heldman, and Australians Kerry Melville Reid and Judy Dalton, launched a campaign for equal prize money two years after the sport's Open Era began in 1968.
The "Original 9" fought with the tennis establishment and broke away to join promoter Gladys Heldman in forming the Virginia Slims circuit, signing $1 contracts on Sept. 23, 1970 despite the threat of being banned from Grand Slams.
Their actions paved the way for the formation of the Women's Tennis Association (WTA) in 1973.
"Dear Original 9. Without your gutsy actions, vision and determination for a better future for women's tennis, we wouldn't be here today," Andreescu, who won the U.S. Open last year, said in an open letter published by the BBC on Thursday.
"When I lifted the U.S. Open trophy last year and got the winner's cheque I know that it is thanks in no small part to you and your incredible bravery that I received the same amount as the men's champion.
"...Your goals were clear: any girl from anywhere would have a place to compete. That women would be recognised for their accomplishments, not only their looks. And that they would be able to make a living playing professional tennis."
Andreescu said the actions of the Original 9 had inspired today's generation of players to continue striving for change.
"What we saw Naomi Osaka do a couple of weeks ago, when she decided not to play a match to protest racial injustice is incredible, as was Coco Gauff's powerful speech at a Black Lives Matter protest to demand change," the 20-year-old Canadian added.
"We owe a huge debt of gratitude to you nine remarkable women, who were ready to jump without a safety net so that girls and women like me would have the chance to dream big and accomplish things."
The National Olympic Committee of Ukraine said he had joined the armed forces in the early days of the war
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