<P> Although the AFL's identity was subsumed by the NFL, the NFL eventually adopted many of the AFL's innovations including the on - field game clock, names on player jerseys, recruiting at small and predominantly black colleges, gate and television revenue - sharing, establishment of southern franchises, and more wide - open offensive rules . </P> <P> Unlike previous armed conflicts such as World War I and World War II, both of which effectively stopped or dramatically reduced the amount of professional football played in the United States, both the AFL and NFL were largely unaffected by the Vietnam War and did not lose a significant number of players to the war draft . There is at least one recorded incidence of the NFL using champagne units to keep its players from being sent overseas (the Dallas Cowboys used the Texas Air National Guard's 147th Fighter Interceptor Group, a well - known champagne unit to shield seven Cowboys players from combat in Vietnam). Bob Kalsu, then a player with the AFL's Buffalo Bills, left the team to serve in Vietnam and died in combat; he was the only casualty of the Vietnam War that the league would sustain . (Don Steinbrunner, who briefly played for the Cleveland Browns, also died in Vietnam, but he left the NFL over a decade before his deployment there .) </P> <P> In the 1970s and 1980s, the NFL solidified its dominance as America's top spectator sport, and its important role in American culture . The Super Bowl became an unofficial national holiday and the top - rated TV program most years . Monday Night Football, which first aired in 1970, brought in high ratings by mixing sports and entertainment . Rule changes in the late 1970s ensured a fast - paced game with lots of passing to attract the casual fan . </P> <P> The World Football League was the first post-merger challenge to the NFL's dominance, and in 1974, successfully lured some top NFL talent to its league and prompted a few rules changes in the NFL . However, financial problems led the league to fold halfway through its 1975 season . Two teams, the Birmingham Vulcans and Memphis Southmen, made unsuccessful efforts to move from the WFL to the NFL . </P>

What is considered the modern era of the nfl
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