Not only was [Roberto] Clemente a baseball player, he was also a Marine. Instead of playing winter ball in Puerto Rico during the 1958-59 off season like the rest of the league, Clemente enlisted in the United States Marine Corps Reserve, spending six years of military commitment as an infantryman. The rigorous conditioning and military training kept him in shape throughout the winter. Clemente remained in the Marine Corps until 1964, but this did not slow down his game. When the Pittsburgh Pirates started spring training for the World Series in 1964, however, the schedule conflicted with Clemente’s military commitment. The Pirates, supported by former state Senator John M. Walker, asked U.S. Senator Hugh Scott to consider Clemente for an early discharge so he would be able to participate in the World Series.
Read the rest: "Roberto Clemente: A Legacy Beyond Baseball" (The National Archives)