With World War I raging throughout Europe, the 1918 baseball season ended prematurely when the United States actively entered the conflict. Although America formally declared war in April of 1917, players did not begin to join the armed forces in significant numbers until Provost Marshall General Crowder issued his "work or fight" order in June of 1918. Contrary to World War II, baseball made no attempt to claim essential employment status on the grounds of aiding public morale, and the government ordered the season cut off on Labor Day, September 2. Personnel losses due to the enlistment or drafting of major leaguers proved to be a huge factor in both pennant races.
Losing Shoeless Joe Jackson, Red Faber, Lefty Williams, Swede Risberg, and Happy Felsch to the war effort caused the defending champion Chicago White Sox to fall to sixth place in the American League. The Boston Red Sox replaced them at the top of the league standings, finishing the campaign with a record of 75-51, 2 ½ games ahead of the second-place Cleveland Indians.
After Boston manager Jack Barry entered the military, team executive Ed Barrow took over control of the club. Barrow completely overhauled his ball club, filling the holes in his lineup by acquiring Stuffy McInnis, Wally Schang, and Bullet Joe Bush from the last-place Philadelphia Athletics. Barrow made his most significant move, though, when he converted Babe Ruth into an outfielder. Manning an outfield spot on those days he didn’t pitch, Ruth ended up batting .300, driving in 66 runs, and tying for the league lead with 11 home runs (even though he accumulated just 317 at-bats). Ruth also compiled a record of 13-7 and an ERA of 2.22 on the mound. Ruth’s dual-effort enabled the Red Sox to capture their third pennant in four years, after which they won their last world championship of the 20th century by defeating the Chicago Cubs in six games in the World Series.
Although Ruth displayed tremendous versatility over the course of the regular season, he was neither the American League’s best hitter, nor its top pitcher. Ty Cobb had an exceptional year for seventh-place Detroit, topping the circuit with a .382 batting average, a .440 on-base percentage, a .515 slugging percentage, and 14 triples. Meanwhile, Walter Johnson continued to excel for the third-place Senators, leading all A.L. hurlers with 23 wins, a 1.27 ERA, 162 strikeouts, and eight shutouts, while placing second in innings pitched (325) and third in complete games (29).
Other notable events from around the league and players who distinguished themselves over the course of the season included:
• April 18 - Cleveland Indians center fielder Tris Speaker turned an unassisted double play against the Detroit Tigers. He duplicated the feat against the Chicago White Sox just 11 days later, setting in the process a franchise record for most unassisted double plays by an outfielder, with four.
• May 14 – Sunday baseball was officially legalized in Washington, D.C. after district commissioners finally rescinded the ban in response to the large increase in the city's wartime population and the need for more recreational activities.
• June 3 - Dutch Leonard tossed the second no-hitter of his career, leading the Boston Red Sox to a 5–0 victory over the Detroit Tigers.
• September 5 - During the seventh inning stretch in Game One of the World Series, a military band played the Star Spangled Banner as a tribute to all servicemen on leave and in attendance. From that point on, the song was played at every World Series outing and every season opener, though it was not yet adopted as the national anthem. The custom of playing it before every game began during World War II, after the installation of stadium speaker systems made it more feasible.
• George Sisler led the American League with 45 stolen bases.
• Babe Ruth extended his World Series scoreless streak to 29 2/3 innings.
• Walter Johnson’s 325 innings pitched placed him in excess of the 300-mark for a record ninth consecutive year.
• Over the course of the season, Johnson completed 15 games that went into extra innings, two of which went 18 innings, one that went 16 innings, and another that went 15 frames.
• Scott Perry posted 20 victories for the last-place A's, who played just 130 games.
- 1918 World Series, American League, Babe Ruth, Boston Red Sox, Chicago Cubs, Dutch Leonard, Ed Barrow, George Sisler, Happy Felsch, Joe Bush, Joe Jackson, Lefty Williams, Red Faber, Scott Perry, Stuffy McInnis, Swede Risberg, Tris Speaker, Ty Cobb, Wally Schang, Walter Johnson