It all started with rival gangs who committed violent crimes in one particular neighbourhood, said Toronto police Chief Bill Blair.
Investigators soon found links to serious criminal activity in other Ontario cities and eventually to parts of Western Canada.
"What is perhaps unique about this particular investigation (is) it revealed a level of mobility among street gangs that we had not yet previously witnessed in this city," Blair said.
"This investigation revealed that that criminal activity spread well beyond the borders of this neighbourhood, well beyond the borders of Toronto, right across Ontario and eventually, right across Canada."
The massive investigation, known as Project Marvel, resulted in early morning raids Tuesday in Ontario, Alberta and B.C., resulting in about 60 arrests and close to 300 charges.
More than 900 officers, including 400 tactical officers, executed 67 search warrants in Toronto, London, Hamilton, Ottawa and other Ontario cities, and in Calgary and Surrey, B.C.
"A quantity of firearms, ammunition, drug monies and associated proceeds of crime were seized," said OPP Supt. Chris White.
Project Marvel, which began in May, involved criminal organization offences, attempted murder, firearms trafficking and importation, drug trafficking, robbery, shootings, prostitution and other crimes, police said.
The Marvel reference comes from the comic-book character names some of the gang members used, police said.
"What's different in this one is how well organized they were and how ruthless they were," White said, describing the two gangs — the Young Buck Killas, also known as the YBK, and the G-siders.
The probe initially involved investigators from Toronto, London, Ont., Ontario's Waterloo Region and Ontario Provincial Police.
But as the investigation matured, it spread to other jurisdictions in Ontario and then to Saskatoon, Calgary, Edmonton, Vancouver, and Fort McMurray, Alta.
Officers from more than 20 police forces, Canada Border Services Agency, and the U.S. Bureau of Alcohol Tobacco, Firearms and Explosives were involved in the investigation.
Sgt. Brett Corey of Windsor police said three warrants were executed in the southwestern Ontario city and one man was charged but no weapons seized.
A 30-year-old man was being been transported to Toronto to face weapons-related charges, Corey said.
More details on the arrests will be released Wednesday, police said.