BRUNSWICK – By the time its offense delivered a knockout punch at the end of the first half Friday night, the defense of the Bowdoin College women’s basketball team had already softened up the Castleton State Spartans.

The Polar Bears forced 18 turnovers and held the Spartans to just 15 point in the opening half. That bought Bowdoin’s offense a little time. When it finished the half with a convincing offensive surge, the Polar Bears were well on their way to a 72-31 win at Morrell Gymnasium.

“It’s something we’ve taken a lot of pride in all year long,” said senior guard Alexa Kaubris of Bowdoin’s defensive effort.

Bowdoin advances to Saturday’s second round of the NCAA Regionals and plays Muhlenberg College, which beat Westfield State in the first game Friday.

“Every game we have is another opportunity to play together,” said Kaubris, the former Dirigio star. “It’s not like we’re going out and playing like we’re afraid to lose. We go out and we’re playing loose and having fun.”

The defense held Castleton at bay in the first half, forcing three shot-clock violations. An early run opened up the quick lead, and when Bowdoin really clicked offensively, it produced 13 straight to build a commanding 38-15 lead.

“They did a great job especially defensively,” said Castleton State coach Tim Barrett. “They took us out of doing everything we wanted to do. “

Katie Bergeron led the Polar Bears (24-4) with 16 points while Ellery Gould added 12. Leah Rubega had nine points and six rebounds while the Polar Bears got five or more points from eight players.

“Our defense kind of bought us some time,” said Bergeron. “When we play good defense, it allows our offense to go. When we get fast breaks, it give us a lot of confidence.”

Bowdoin has won at least one tourney game in its previous eight appearances. That gave the Polar Bears a distinct advantage over the Spartans (17-12), which were making their first-ever appearance in the NCAA Division III tourney.

Castleton’s turnovers hindered any offensive consistency in the opening half. After getting the first basket of the game, Castleton State went six minutes without a field goal. The Spartans also had other droughts, including another seven minutes without a field goal midway through the half and over four minutes without a point late in the half.

Bowdoin struggled to hit shots early but ran off 11 straight to build a quick 11-2 lead. A pair of baskets by Bergeron and hoops from Kaubris and Rubega made it 8-2. Then a 3-pointer by Maria Noucas made it 11-2.

“We had to have confidence in our shots and keep shooting,” said Bowdoin coach Adrienne Shibles. “I could see us tensing up. That’s where our defense was really fantastic and kept us in the game.”

The Spartans got within 12-7 after a 3-pointer by Jessica Banks, but the Polar Bears added to the lead when Ellery Gould and Bergeron hit back-to-back 3s. Then Rubega scored five straight in the post to spark the 13-0 run. After a Bergeron drive, Jill Henrikson drilled a 3-pointer for make it 33-11.

“At that point, we had a lot of confidence in each other and it showed,” said Kaubris. “We were having a lot of fun and smiling out there.”

Things didn’t get much better for Castleton in the second half. The Spartans were held to just five points over the first 12:30, and Bowdoin used a 10-0 run to build a 40-point led. Gould had five points during that stretch.

“As they started getting stops defensively, we kind of let down defensively,” said Barrett. “Credit their offense, they executed better at the end of the first half.”