The NFL reached the West Coast for the first time when the defending champion Cleveland Rams moved to Los Angeles for the 1946 season. After stabilizing for the first time in the late 1930s, the league was mostly unchanged in its third decade except for adjustments made during World War II.
The war led to more than 1,000 players interrupting or postponing their pro football careers. As a result, the 10-team league went down to eight for one season, in 1943. The Cleveland Rams suspended operations, while the Philadelphia Eagles and Pittsburgh Steelers merged for the season.
The count went back to 10 in 1944 with the return of the Rams and the addition of the Boston Yanks, while the Steelers merged with the Chicago Cardinals just for that season. The combined team, called Card-Pitt, went 0-10.
After the war, the NFL service roster, limited to men who played in league games, totaled 638. Of those, 21 died in action.
Before the better-known AFL merger of 1970, the All-America Football Conference laid the foundation for what amounted to the NFL's first merger. The AAFC played the final four seasons of the 1940s, with three of the seven remaining teams joining the NFL in 1950: the Cleveland Browns, San Francisco 49ers and Baltimore Colts.