National Football League and its rivals south of the border. While the presence of American players (later called "imports" and today officially known as "internationals") would play a decisive role in bringing the calibre of the top Western teams to a level approaching that of the top clubs in the East, it further exacerbated the disparity within the Western provincial unions. Western Interprovincial Football Union (1936–1960) In a bid to stabilize and improve the quality of the game in Western Canada, the Winnipeg Blue Bombers of the MRFU, the Regina Roughriders of the SRFU and the Calgary Bronks of the ARFU decided to break away from their provincial unions and form a new elite competition, the Western Interprovincial Football Union. The MRFU ceased operations almost immediately. However, the SRFU, ARFU and WCRFU all initially resisted the formation of the new league. The WCRFU insisted that Western teams could only compete for the Grey Cup by remaining in their respective provincial unions – meaning that the new WIFU faced the threat of being branded an "outlaw" league. Calgary and Regina reluctantly agreed to play in both the WIFU and their respective provincial unions for the 1936 season. Regina would go on to win the first Western championship following the formation of the WIFU, only to find themselves barred by the CRU from competing in the Grey Cup. The WIFU had ignored a rule implemented by the CRU immediately following Winnipeg's first Grey Cup win strictly limiting the use of American players in Canadian football. By the following season, the ARFU and SRFU had both collapsed. The North Western League was organized in an effort to replace the Albertan and Saskatchewan unions, leaving the BCRFU as the only purely provincial union operating in Western Canada. The WCRFU subsequently agreed to a format whereby the BCRFU and NWL champions would have the right to challenge the WIFU champion for the right to represent the West in the Grey Cup. Ultimately, no such challenge would be issued by either league, neither of which survived World War II. The WIFU expanded to four teams when the Edmonton Eskimos joined in 1938. The Eskimos lasted only two years before withdrawing following the outbreak of the war. The Bronks left the following year, but were replaced by the Vancouver Grizzlies following the collapse of the BCRFU. This arrangement lasted only one season, with the WIFU suspending operations