Son Heung-min led Tottenham as it overwhelmed Borussia Dortmund during the second half of their Champions League match Wednesday, setting Spurs on their way to a 3-0 victory in the first leg in London.

After being on the back foot throughout the first half, Tottenham took control against Dortmund, the German league leaders, once Son scored two minutes into the second half. It was Son’s fourth goal in four games.

Tottenham added two late goals three minutes apart to complete the rout and take a commanding lead. The return leg is March 5 in Germany.

Defender Jan Vertonghen and striker Fernando Llorente scored in the final 10 minutes. Both teams were without their top attacking threats, as Marco Reus, the Dortmund captain, and Tottenham’s Harry Kane, were injured.

It was a night to forget for the American Christian Pulisic, who will be playing in London for Chelsea next season, and Jadon Sancho, the 18-year-old former Manchester City attacker from Britain who faded in the second half.

“We lost focus,” Sancho said. “Son is a good player but hopefully we can handle him better in the second leg.”

It was the third setback in a week for Dortmund, which was knocked out of the German Cup by Werder Bremen and then drew with Hoffenheim in league play.

REAL MADRID 2, AJAX 1 With a little help from the video assistant referee, which overturned a goal for the first time in Champions League play, Real Madrid overcame a spirited Ajax in Amsterdam to take a big step toward the quarterfinals.

The substitute Marco Asensio scored the winner in the 87th minute as Real Madrid, winner of the last three Champions Leagues, recovered in the second half after being outplayed by an underdog Ajax squad before the break at a packed Johan Cruyff Arena.

Ajax had appeared to be on course for a draw when Hakim Ziyech shot under Thibaut Courtois in the 75th minute to cancel out Karim Benzema’s opener 15 minutes earlier.

Ajax, a four-time European champion that last won the title in 1995, dominated the first half and looked to have taken the lead in the 37th minute on Nicolás Tagliafico’s header, but V.A.R. overturned the goal because Dusan Tadic was ruled to have interfered with Courtois.

Kasper Dolberg came close to tying the score on a break in stoppage time, but Courtois got a hand up to block the awkward shot.