Russian challenger Aleksandra Goryachkina earned her first ever victory over China's defending champion Ju Wenjun in game five of the Women's World Chess Championship in Shanghai.
Goryachkina, who had lost the fourth game after three opening draws, thus restored the score to 2½-2½ after five games, with only one left to be played in the current Chinese venue.
The remaining six games in this International Chess Federation (FIDE) event will be fought on her "home ground" in Vladivostok between January 15 and 23.
A tiebreak, if needed, and the Closing Ceremony are scheduled on January 24.
Goryachkina said she was relieved and happy to be back in the match.
Ju agreed that while today's result was disappointing, it was a logical conclusion and the overall score reflected the match thus far.
Before today, the 21-year-old Russian had never beaten the 28-year-old, who has held the world title since May 2018.
A World Champion resigning a game is always a rare sight.— International Chess Federation (@FIDE_chess) January 11, 2020
Ju Wenjun extends her hand and congratulates Aleksandra Goryachkina at the end of the fifth game.
📸: @MishaFriedman #WomenChessMatch pic.twitter.com/JFy301peNX
But she had already shown signs of being able to impose pressure on the Chinese champion before today's breakthrough, which followed a rest day.
In today's encounter, after mutual early mistakes, the game appeared to be heading for a draw, until a serious blunder by Ju allowed White to consolidate her advantage and convert it into a full point 15 moves later.
The winner of the 2020 title will earn €500,000 (£427,000/$558,000) - the biggest prize ever awarded in women's chess.
The event has returned to a series of matches between two players, as with the Men's World Championship.
Ju first won the title over 10 games against compatriot Tan Zhongyi in May 2018, but had to defend her crown in a 64-player tournament in Khanty-Mansiysk in Russia in November of that year.
She did so successfully, with Goryachkina coming through last year's Candidates Tournament to earn the right to face her.