The organization that came to prominence in the rapidly changing game in the 1970s appeared 20 years earlier out of the ashes of the short-lived American Baseball Guild, which had a similar structure. When the pension won by that group was threatened by the owners in 1953, the player representatives of the 16 teams hired attorney J. Norman Lewis to fight the threat. That battle was won, but the new union was largely neglected until Marvin Miller revamped it starting in 1966.
Within two years the Association had signed the first Basic Agreement with the owners. Progress at first was cautious; for instance, the union advised Curt Flood against challenging baseball’s reserve clause. But an unprecedented, albeit brief, strike at the beginning of the 1972 season gave notice that the players had a unity not seen since the 1890 Players’ League revolt, and when the owners tried to fight back in 1981, a longer strike in mid-season forever changed the image of the game. The concessions made by the owners in the face of these two strikes revamped player-owner relations completely: arbitration, free agency, the right of veterans to veto trades, and vastly higher salaries. Miller trained his assistant and eventual successor, Donald Fehr, before retiring in 1984; Fehr chose as his assistant former player Mark Belanger.