Phoenix police Officer Mercedes Fortune wanted to crack the "Rock Block," a south Phoenix area police say is ridden by rampant narcotics sales, home invasions and murders.

Fortune got her wish as a lead investigator in a two-year probe that resulted in more than 40 arrests Tuesday of suspected gang members who had directed crack or "rock" cocaine sales in the South Mountain Village area.

More than 300 officers from 10-plus agencies fanned out at 4 a.m. Tuesday to make arrests and seize drugs. A total of 71 indictments were made in the case.

"The many good neighbors in this area deserved to live without fearing gang activity, drug sales and shootouts," said Assistant Chief Kevin Robinson, who helped set the probe into motion.

The investigation mainly targeted an area from 16th to 32nd streets between the Salt River bottom and Roeser Road. Arrests were made from east Mesa to Avondale.

Fortune, 38, served for 11 years with the Los Angeles Police Department, often patrolling the tough South Central LA neighborhoods where she grew up. She came to Phoenix in 2007 to be near her parents, who had moved to the Valley. When hired onto the Phoenix force, she wanted to serve in the South Mountain Precinct.

It is a precinct of neighborhoods where poverty, joblessness and crime rub shoulders with upper-middle-income areas of new homes and good schools. It also has seen a string of troubling incidents in the past year: the unsolved slaying of a well-regarded sergeant, accusations by a city councilman of civil-rights violations, the indictment of several officers in an off-duty pay scam, and the indictment of a patrol officer on homicide charges.

Nearly the entire layer of upper management in the precinct was replaced in the past year. The precinct is now led by Commander Chris Crockett and six new lieutenants.

"We have never stopped serving the people of South Phoenix, and we are glad to be able to demonstrate our dedication to bringing justice to this area," said Lt. Sean Connelly, who helped supervise the probe and called it a "major payday."

Officer Clinton David Swick, one of those at the center of the probe, said that a driving force behind it was that "we were taking down a few crack houses at a time. And were we making a real impact? No. We needed to do something different."

Enter Fortune.

"Shortly after I came to the precinct, I was put on a Neighborhood Enforcement Team and soon was working with people like Dave Swick," she said. "Gradually, looking at the big picture became easier. I realized that though we had a bunch of guys in separate locations selling drugs, they were also talking to each other. There was organization, not just a bunch of individual crack houses operating in isolation. I thought we could find the links."

Fortune in August 2009 went to Connelly and Sgt. Jesse Abernathy with a plan.

"I said to them, 'Let's start connecting who knows who and who is talking to whom,' " she said. "We'll do it through surveillance, wiretaps, examining previous investigations and files, and we'll build a picture."

Connelly and Abernathy knew well that Fortune and Swick and other investigators would be up against decades of success by a violent gang that ran the area drug trade: the Broadway Gangsters.

"The Broadway Gangsters have been around so long they are a generational gang," Abernathy said. "A man is in it, his brothers are in it, his son is in it, his nephews and cousins are in it. All of them know each other and trust each other . . . and trust only each other. A guy grows up in the neighborhood, becomes a BWG and it's his life."

Fortune, Swick and other officers thought they could break through the gang's wall of silence via surveillance, intensive talks with sources and warrants for wiretaps.

A tragic incident gave new urgency to the investigation. In July 2010, Chandler drug detectives conducted an undercover operation that took them to a house in the Broadway Gangsters' domain. They pretended to be making a drug sale.

They were armed with service pistols. The gangsters who came to "buy" had a small arsenal that included a shotgun, an AK-47 and various handguns.

When four armed Broadway Gangsters entered the house, "all hell blew up," in the words of one suspect who later described it to police. Chandler Officer Carlos Ledesma was killed by four shots from an assault rifle. Two suspects also were killed. Two other officers and a suspect were injured.

"When Officer Ledesma was killed, that brought more attention and concern to the area and it also brought Drug Enforcement Administration officers to the neighborhood," Fortune said. "A partnership between us and the DEA then began, and it worked. It was two NET squads and nine DEA officers."

It was a powerful partnership. Over the past year, evidence mounted of a wide-ranging drug conspiracy. Police allege that cocaine in powder form was being imported from the Mexican city of Culiacan. A dealer with ties to the Broadway Gangsters turned it into crack cocaine and sold it to upper-level members of the gang, police allege, who then distributed it to gangsters stationed in rented houses in the area.

The O.G.s - or Original Gangsters, as the older Broadway Gangsters called themselves - at the top didn't worry much when younger members were netted in drug raids. It was the O.G.s that Phoenix police and the DEA most wanted to snag, because they were directing the drug traffic and making significant profits, police allege.

By the end of last week, investigators felt they had sufficient evidence in hand. The information was taken to the Arizona Attorney General's Office, whose prosecutors helped plan the sweep. Arrangements were made for the massive bust that began early Tuesday.

Tuesday night, officers took inventory of bales of marijuana, bricks of cocaine, bundles of cash and other contraband, while prosecutors prepared charges.

"I grew up in an area like this in South Central LA," Fortune said. "When there is this much crime, it is the good citizens who suffer most."

"We're doing this for the citizens," she said. "My parents were laborers and we could only afford to live in a tough neighborhood. That gives me sympathy for people who live in a difficult area, and this investigation fulfills my desire to give back."