Background: Vincent Kennedy McMahon was born on August 24, 1945 in Pinehurst, North Carolina, the younger son of Victoria (Askew) and Vincent James McMahon. His father left the family when McMahon was still a baby and took his elder son Rod with him, therefore McMahon did not meet him until age twelve. McMahon's paternal grandfather was promoter Roderick James "Jess" McMahon, whose parents were Irish emigrants from County Galway. His paternal grandmother, Rose Davis, was also of Irish descent.
Context: On February 21, 1980, McMahon officially founded Titan Sports, and the company's headquarters were established in South Yarmouth, Massachusetts, using the now defunct Cape Cod Coliseum as a home base for the company. At the time of his purchase of the WWF, professional wrestling was a business run by regional promotions. The various promoters shared an understanding that they would not invade each other's territories, as this practice had gone on undeterred for decades; McMahon had a different vision of what the industry could become. In 1983, the WWF split from the National Wrestling Alliance a second time, after initially splitting from them in 1963 before rejoining them in 1971. The NWA was the governing body for all the regional territories across the country and as far away as Japan.  He began expanding the company nationally by promoting in areas outside of the company's Northeast U.S. stomping grounds and by signing talent from other companies, such as the American Wrestling Association (AWA). In 1984, he recruited Hulk Hogan to be the WWF's charismatic new megastar, and the two quickly drew the ire of industry peers as the promotion began traveling and broadcasting into rival territories. Nevertheless, McMahon (who still also fronted as the WWF's squeaky clean babyface announcer) created The Rock 'n' Wrestling Connection by incorporating pop music stars into wrestling storylines. As a result, the WWF was able to expand its fanbase into a national mainstream audience as the promotion was featured heavily on MTV programming. On March 31, 1985, he ran the first WrestleMania at Madison Square Garden, available on closed circuit television in various markets throughout the U.S.  During the late 1980s, McMahon shaped the WWF into a unique sports entertainment brand that reached out to family audiences while attracting fans who had never before paid attention to pro wrestling. By directing his storylines towards highly publicized supercards, McMahon capitalized on a fledgling revenue stream by promoting these events live on PPV television. In 1987, the WWF reportedly drew 93,173 fans to the Pontiac Silverdome (which was called the "biggest crowd in sports entertainment history") for WrestleMania III, which featured the main event of Hulk Hogan versus Andre the Giant.
Question: What year did they decide not to invade each other's territories?

Answer:
this practice had gone on undeterred for decades;