CHICAGO — The Chicago Bears awoke after a lethargic first half, scoring three third-quarter touchdowns — two of them on runs by Matt Forte following takeaways — to come from behind and defeat the Tampa Bay Bucs, 21-13, Sunday at Soldier Field.

It was the second straight game in which the Bears, who haven’t scored in the first quarter in six games in a row, spotted an opponent a 10-0 lead and rallied to win by the same 21-13 score.

The Chicago formula of winning with takeaways was familiar to Tampa Bay coach Lovie Smith, who led the Bears to the NFC championship in 2006 but was fired following the 2012 season. Under Smith, the Bears’ defense worked hard at forcing turnovers and was always among the league leaders.

Until Sunday, it was not that way this season; the Bears had forced just 14 takeaways in 10 games before getting four against the Bucs.

The Bears needed the help from their defense after Tampa Bay held them to 68 yards and three first downs in the first half while building a 10-0 halftime lead. As it was, Chicago’s offense finished with only 204 yards.

After Chicago drove 58 yards for a touchdown on its first possession after halftime, the defense took control, helped by the poor play of Buccaneers quarterback Josh McCown, who was the Chicago backup a year ago.

McCown repeatedly showed a lack of pocket presence when being pressured from behind and overthrowing open receivers when he had time, and both of those things did in the Bucs.

First, McCown, running out of the pocket on a 2nd-and-8 play, was unaware of defensive end David Bass bearing down on him. Bass knocked the ball loose from behind, rookie linebacker Christian Jones recovered, and, one play later, Forte scored on a 13-yard run for a 14-10 Chicago lead.

On the first play after the kickoff, McCown threw another of his too-high passes, running back Charles Sims leaped but it went off his hands and was intercepted by safety Ryan Mundy at the Tampa Bay 15-yard line. Forte ran the ball four straight times, scoring from the one for a 21-10 lead.

The Bucs had one last chance after closing the gap to eight points but were stopped on 3rd-and-1 and 4th-and-1 plays from the Bears’ 36-yard line with two minutes remaining.

Chicago’s comeback began when three straight plays went for first downs early in the third quarter, matching the Bears’ first half total of first downs. There was an 11-yard pass from Cutler to Brandon Marshall, a 13-yard run by Forte and a 26-yard pass from Cutler to tight end Martellus Bennett, who made a nifty leaping catch.

On 3rd-and-goal from the two, Cutler threw a touchdown pass to Alshon Jeffery to narrow the Bucs’ lead to 10-7.

Tampa Bay scored early in the second quarter, a 19-yard pass from McCown to Mike Evans set up by a fumble recovery. Patrick Murray added a field goal just before halftime.

NOTES: The Bucs had to play without LB Lavonte David (hamstring), who shared the league lead in tackles — with more than twice as many as any other player on the Bucs — including a team-high 14 tackles for losses. … With RT Jordan Mills (ribs) unable to play, the Bears have had their season-opening offensive line available for only one other game this year. … FB Javorskie Lane of the Bucs was knocked out of the game with a right ankle injury early in the second quarter. … The Bears had to play the second half without two defensive starters who sustained first-half injuries — LB Lance Briggs (groin) and CB Kyle Fuller (knee).