𝗢𝗻 𝘁𝗵𝗶𝘀 𝗱𝗮𝘆 𝗶𝗻 1944, 𝗝𝗮𝗰𝗸𝗶𝗲 𝗥𝗼𝗯𝗶𝗻𝘀𝗼𝗻, 𝗮 𝗨.𝗦. 𝗔𝗿𝗺𝘆 𝘀𝗼𝗹𝗱𝗶𝗲𝗿 𝘄𝗵𝗼 𝘄𝗼𝘂𝗹𝗱 𝗴𝗼 𝗼𝗻 𝘁𝗼 𝗯𝗿𝗲𝗮𝗸 𝘁𝗵𝗲 𝗰𝗼𝗹𝗼𝗿 𝗯𝗮𝗿𝗿𝗶𝗲𝗿 𝗶𝗻 𝗠𝗮𝗷𝗼𝗿 𝗟𝗲𝗮𝗴𝘂𝗲 𝗕𝗮𝘀𝗲𝗯𝗮𝗹𝗹, 𝗿𝗲𝗳𝘂𝘀𝗲𝗱 𝘁𝗼 𝗺𝗼𝘃𝗲 𝘁𝗼 𝘁𝗵𝗲 𝗯𝗮𝗰𝗸 𝗼𝗳 𝗮𝗻 𝗔𝗿𝗺𝘆 𝗯𝘂𝘀, 𝗹𝗲𝗮𝗱𝗶𝗻𝗴 𝘁𝗼 𝗵𝗶𝘀 𝗯𝗲𝗶𝗻𝗴 𝗰𝗼𝘂𝗿𝘁-𝗺𝗮𝗿𝘁𝗶𝗮𝗹𝗲𝗱.
In 1942, Robinson was drafted and assigned to a segregated Army cavalry unit in Fort Riley, Kansas. Having the requisite qualifications, Robinson and several other black soldiers applied for admission to an Officer Candidate School (OCS) then located at Fort Riley. Although the Army's initial July 1941 guidelines for OCS had been drafted as race neutral, few black applicants were admitted into OCS until after subsequent directives by Army leadership. As a result, the applications of Robinson and his colleagues were delayed for several months. After protests by heavyweight boxing champion Joe Louis (then stationed at Fort Riley) and the help of Truman Gibson (then an assistant civilian aide to the Secretary of War), the men were accepted into OCS. The experience led to a personal friendship between Robinson and Louis. Upon finishing OCS, Robinson was commissioned as a second lieutenant in January 1943.
After receiving his commission, Robinson was reassigned to Fort Hood, Texas, where he joined the 761st "Black Panthers" Tank Battalion. While awaiting results of hospital tests on the ankle he had injured in junior college, Robinson boarded an Army bus with a fellow officer's wife; although the Army had commissioned its own unsegregated bus line, the bus driver ordered Robinson to move to the back of the bus. Robinson refused. The driver backed down, but after reaching the end of the line, summoned the military police, who took Robinson into custody. When Robinson later confronted the investigating duty officer about racist questioning by the officer and his assistant, the officer recommended Robinson be court-martialed. After Robinson's commander in the 761st, Paul L. Bates, refused to authorize the legal action, Robinson was summarily transferred to the 758th Battalion—where the commander quickly consented to charge Robinson with multiple offenses, including, among other charges, public drunkenness, even though Robinson did not drink.
By the time of the court-martial in August 1944, the charges against Robinson had been reduced to two counts of insubordination during questioning. Robinson was acquitted by an all-white panel of nine officers. The experiences Robinson was subjected to during the court proceedings would be remembered when he later joined MLB and was subjected to racist attacks. Although his former unit, the 761st Tank Battalion, became the first black tank unit to see combat in World War II, Robinson's court-martial proceedings prohibited him from being deployed overseas; thus, he never saw combat action.
After his acquittal, he was transferred to Camp Breckinridge, Kentucky, where he served as a coach for army athletics until receiving an honorable discharge in November 1944. While there, Robinson met a former player for the Kansas City Monarchs of the Negro American League, who encouraged Robinson to write the Monarchs and ask for a tryout. Robinson took the former player's advice and wrote to Monarchs' co-owner Thomas Baird.
