Louis Armstrong thought enough of Miller to carry around his recordings, transferred to seven-inch tape reels when he went on tour. "[Armstrong] liked musicians who prized melody, and his selections ranged from Glenn Miller to Jelly Roll Morton to Tchaikovsky." Jazz pianist George Shearing's quintet of the 1950s and 1960s was influenced by Miller: "with Shearing's locked hands style piano (influenced by the voicing of Miller's saxophone section) in the middle [of the quintet's harmonies]". Frank Sinatra and Mel Tormé held the orchestra in high regard. Tormé credited Miller with giving him helpful advice when he first started his singing and song-writing career in the 1940s. Tormé met Glenn Miller in 1942, the meeting facilitated by Tormé's father and Ben Pollack. Tormé and Miller discussed "That Old Black Magic", which was just emerging as a new song by Johnny Mercer and Harold Arlen. Miller told Tormé to pick up every song by Mercer and study it and to become a voracious reader of anything he could find, because "all good lyric writers are great readers." In an interview with George T. Simon in 1948, Sinatra lamented the inferior quality of music he was recording in the late forties, in comparison with "those great Glenn Miller things" from eight years earlier. Frank Sinatra's recording sessions from the late forties and early fifties use some Miller musicians. Trigger Alpert, a bassist from the civilian band, Zeke Zarchy for the Army Air Forces Band and Willie Schwartz, the lead clarinetist from the civilian band back up Frank Sinatra on many recordings. With opposite opinion, fellow bandleader Artie Shaw frequently disparaged the band after Miller's death: "All I can say is that Glenn should have lived, and 'Chattanooga Choo Choo' should have died." Clarinetist Buddy DeFranco surprised many people when he led the Glenn Miller Orchestra in the late sixties and early seventies. De Franco was already a veteran of bands like Gene Krupa and Tommy Dorsey in the 1940s. He was also a major exponent of modern jazz in the 1950s. He never saw Miller as leading a swinging jazz band, but DeFranco is extremely fond of certain aspects of the Glenn Miller style. "I found that when I opened with the sound of 'Moonlight Serenade', I could look around and see men and women weeping as the music carried them back to years gone by." De Franco says, "the beauty of Glenn Miller's ballads [...] caused people to dance together."
In 1942, at the peak of his civilian career, Miller decided to join the war effort, forsaking an income of $15,000 to $20,000 per week in civilian life ($236,289 to $315,052 in 2020 dollars), including a home in Tenafly, New Jersey. At 38, Miller was too old to be drafted and first volunteered for the Navy but was told that they did not need his services. Miller then wrote to Army Brigadier General Charles Young. He persuaded the United States Army to accept him so he could, in his own words, "be placed in charge of a modernized Army band". After he was accepted into the Army, Miller's civilian band played its last concert in Passaic, New Jersey, on September 27, 1942, with the last song played by the Miller civilian band being "Jukebox Saturday Night"—featuring an appearance by Harry James on trumpet. His patriotic intention of entertaining the Allied Forces with the fusion of virtuosity and dance rhythms in his music earned him the rank of captain and he was soon promoted to major by August 1944.
Miller reported at Omaha on October 8, 1942, to the Seventh Service Command as a captain in the Army Specialist Corps. Miller was soon transferred to the Army Air Forces. Captain Glenn Miller served initially as assistant special services officer for the Army Air Forces Southeast Training Center at Maxwell Field, Montgomery, Alabama, in December 1942. He played trombone with the Rhythmaires, a 15-piece dance band, in both Montgomery and in service clubs and recreation halls on Maxwell. Miller also appeared on both WAPI (Birmingham, Alabama) and WSFA radio (Montgomery), promoting the activities of civil service women aircraft mechanics employed at Maxwell.