Dear SoCal,
re: “So by went on strike, you don’t mean the players walked out in a union action, correct?”
THAT is exactly what they did! And in doing so, the NFL head offices refused to send already played games on film, to the troops overseas.
In 1972, there was no such thing as videotape machines, for the public.
They were reel-to-reel films.
Wikipedia says there were strikes in 1970 and 1974, neither of which affected league games, I was 15 in 1972 and have no memory of any NFL games cancelled as a result of any work stoppage.