Vic Fangio got his first NFL job with the New Orleans Saints in 1986, when he was 28 years old. He spent nine seasons there as the team’s linebackers coach, and during that time, Fangio developed a friendship with Saints general manager and longtime NFL executive Jim Finks. More than once, Finks told the young coach that if he ever had the chance, he should try to land a job in Chicago. It was a sports town, Finks used to say, one that loved its Bears. But more importantly, it was a city that loved defense.

In 2015, almost 30 years after entering the league and receiving Finks’s advice, Fangio finally landed in the Windy City. Then–Bears head coach John Fox hired him as the team’s defensive coordinator, and upon arriving in Chicago, Fangio found a fan base that was dying to embrace the brand of football he wanted to play. Despite the fame that past Bears defensive masterminds have achieved, Fangio jokes that he’s been recognized on the street only once since taking the job, at a gas station near his home. But as teams around the NFL circle him for their head-coaching vacancies, it’s clear just how beloved Fangio and his work have become. Fangio has constructed the league’s most ferocious defense this season, and behind Khalil Mack’s and Eddie Jackson’s strong performances, it feels like a unit that uniquely belongs in Chicago.

It’s hard to explain why defense seems to matter more to Chicago than to other franchises. Plenty of NFL teams are known for their past stonewall defenses and the legendary players who led them: The Steel Curtain remains synonymous with Pittsburgh; the Ravens have been defined by defense since moving to Baltimore in 1996. But over time, the work of Antonio Brown and Ben Roethlisberger has shifted the Steelers’ identity. And though Baltimore has produced some of the league’s best units of the past 20 years, the team hasn’t been around any longer than that. For the Bears, though, all of their great moments over the past half-century have been driven by defense. When Chicago won the NFL championship in 1963, the defense allowed a league-best 10.3 points per game. The 1985 Bears are still largely considered the greatest defense of all time. In Chicago, defense just feels … right. And that’s why the 2018-19 edition of this team fits so comfortably into the franchise’s history. “When you’re in Chicago,” says former Bears cornerback Charles Tillman, “and it’s third down, and it’s 10 below zero, and the crowd is into it, and there’s some big chubby guy with his shirt off who’s trying to get the fans into it, and his beer is frozen, that’s Chicago football.”

Tillman was drafted by Chicago in 2003, and in those days, he says rookies were almost immediately indoctrinated with Bears lore. Dwayne Joseph, the former Bears director of player development (and current Eagles director of pro scouting), would put together an annual presentation for first-year players on the relevant moments from the organization’s past—a “history lesson, Chicago Bears 101” as Tillman describes it. And plenty of those lessons revolved around defense. They discussed Bill George. Doug Atkins. Dick Butkus. Mike Singletary. Dan Hampton. The franchise’s past was lined with immortal defenders, and as an incoming rookie, Tillman immediately understood that Chicago was the perfect place to be embraced as a defensive player. “It might be different in Indianapolis or Green Bay, where they want to see Aaron Rodgers throw touchdowns,” Tillman says. “Here, they want to see defense.”

Bears Pro Bowl defensive tackle Akiem Hicks has been with the team for three seasons, and from the start, he recognized that same defensive fanaticism—one that’s only been ratcheted up this year. It’s tempting to say that Khalil Mack’s arrival via trade on Labor Day weekend is what transformed Chicago’s defense from a steady unit into the juggernaut it’s become, but the process had begun long before he arrived.

“When you’re in Chicago, and it’s third down, and it’s 10 below zero, and the crowd is into it, and there’s some big chubby guy with his shirt off who’s trying to get the fans into it, and his beer is frozen, that’s Chicago football.” —Charles Tillman, former Bears cornerback

Chicago finished fourth in the NFC North last season with a 5-11 record, which led to the firing of Fox. But there was one bright spot on the team: Fangio’s defense. The Bears allowed just 20 points per game in 2017 (the ninth-best mark in the league) despite dealing with an onslaught of injuries for the second straight season. When first-year head coach Matt Nagy was hired last January, he recognized the potential on that side of the ball and the heights that group could reach if it was healthy. So to maintain continuity, Nagy retained Fangio and asked him to build on the progress he’d already made with his defense.

Long before trading for Mack, Fangio’s group looked like one of the league’s most complete units. Safety Eddie Jackson had a breakout rookie season in 2017. His counterpart, Adrian Amos, was already one of the more underrated players in football. And this offseason, general manager Ryan Pace retained all three starting cornerbacks from last year’s team—Kyle Fuller, Prince Amukamara, and slot man Bryce Callahan—in free agency. Hicks emerged as a star on the interior of the defensive line last season, along with recently extended nose tackle Eddie Goldman. And at linebacker, the Bears added 2018 first-round draft pick Roquan Smith next to Danny Trevathan. As the Bears arrived in Bourbonnais, Illinois, for training camp in July, they had few obvious weaknesses. “When I’m going through OTAs and I see my linebacker running 30 miles an hour to cut something off in the flat, you start to get excited about that,” Hicks says of Smith. “You think, ‘Man, we’ve got something brewing here.’ … Nagy may not like me saying this, but we were dominating the offense.”

Hicks says the Bears defense was already turning the corner before they landed one of the NFL’s best players. With the addition of Mack, they became unstoppable. “When we stepped in this year, we had goals of accomplishing way more,” Hicks says. “Then we get this cherry on top with a super-elite pass rusher. Notice I said ‘super elite.’ He’s different.”

From Mack’s first few snaps in a Bears uniform, it was clear Chicago had poached a force from the Raiders. He was unblockable in Week 1 against the Packers, causing his first of six forced fumbles on the season and returning an interception for a touchdown. “I felt it when we were up 20-0 against Green Bay. Did we finish that game out? No,” Hicks says of the Packers’ eventual comeback to win 24-23. “But I knew at that point, if we can get up 20-0 on Aaron Rodgers, who can’t we do it to?”

As Mack’s dominance has extended throughout the season, it’s been hard not to compare him to some of the other great Bears linebackers and pass rushers in history, like Singletary, Brian Urlacher, Richard Dent, and Wilber Marshall. But look beyond the giant legacy of that ’85 team, and it’s clear this defense also embodies traits that made some of Chicago’s less-famous defenses successful.

During Tillman’s career, the Bears were fueled by takeaways. The first dominant unit of his tenure arrived in 2005, Tillman’s third season in the league and Lovie Smith’s second as the Chicago head coach. That year, the Bears allowed just 4.4 yards per play, which led the NFL, and they intercepted 24 passes, tied for the second-best mark in the NFL. The following season, en route to a 13-3 finish and a trip to the Super Bowl, the Bears created a league-high 44 turnovers, including 24 interceptions. In 2012, Chicago once again led the NFL in defensive DVOA and generated another 44 takeaways. Turnover margins tend to regress from season to season, even for great defenses, but during Smith’s nine-year tenure as head coach, his teams consistently finished near the top of the league in that figure. To hear Tillman tell it, generating turnovers for that unit was akin to breathing. It wasn’t just a mind-set—it was an obsession. In practice, every interception or fumble was returned all the way to the end zone. Incomplete passes were scooped up and run back every time. The Bears regularly did drills that forced defenders to quickly transition from cornerback to ball carrier, linebacker to blocker. “It was something that you did, like going to the bathroom and washing your hands,” Tillman says. “You get ready to eat, you grab a fork. You get in a car, you put your foot on the brake, and you put it in drive. There are certain things that you do every day. That’s how we were with taking the ball away.”

This year’s Bears have adopted the same mind-set, complete with a Smith-era-like dedication to turning every interception or fumble into six points the other way. Chicago has generated 36 turnovers this season, five more than any other team. Fangio’s crew has also scored an NFL-leading six touchdowns on those turnovers. Three of those TDs were recorded by Jackson, who’s taken up the mantle previously held by players like Mike Brown as the Bears defender who’s most likely to find the end zone on any given play.

Despite the consistency developed under Smith, history says that the Bears defense is unlikely to repeat this type of performance next season. Fangio will likely be hired away as a head coach after the playoffs. Amos and Callahan will be free agents this spring, and Chicago’s cap limitations may hinder the team from retaining them. The Bears defense probably won’t score six touchdowns next season, or intercept 27 passes. And in an era when Patrick Mahomes II can throw 50 touchdown passes in his second season, building a team around stellar defense likely isn’t the best route to contend for championships year after year.

But this season, the Bears have been easy to love in part because of how familiar they feel to their city. When Mack and Co. line up against the Eagles at Soldier Field this Sunday afternoon, in the frigid Chicago air, everything about Bears football will feel like it’s fallen back into place. Even if it’s only for another game—or two, or three—seeing that fearsome defensive group take the field will give Bears fans a familiar feeling that they’ve been missing for some time.