Dear Mori Ogai,
Thank you for posting your request on History Hub!
We are unaware of any comprehensive list of World War II battlefield promotions or commissions. Information about military promotions may be located at various levels from individual units to theaters of operation to branches of service and more.
The estimate of 25,500 battlefield promotions that you found online includes a reference to a ”board of officers reporting to the Commanding General of the European Theater.” That organization is the War Department’s General Board of the U.S. Forces, European Theater. We searched the National Archives Catalog and located 6 series in the Records of Headquarters, European Theater of Operations, United States Army (World War II) (Record Group 498) that were created by the General Board and that may include information related to battlefield promotions. For example, the series Records Relating to Operations Reports, 1945-1946 contains 2 files related to appointments and promotions, and the series General Correspondence Files, 1945-1946 includes information about personnel assignments. These records have not been digitized. Please contact the National Archives at College Park - Textual Reference (RDT2) at firstname.lastname@example.org for access to and information about these records.
We suggest that you use The National Archives Catalog to review additional potentially relevant records created by various sub-sections and offices of the General Board. You may use the Catalog to search for records related to battlefield promotions and commissions as well. The Advanced Search feature to narrow your results by time period, type of record, and so forth. Please contact the National Archives reference unit listed in each Catalog description for assistance with those particular records.
Due to the COVID-19 pandemic and pursuant to guidance received from the Office of Management and Budget (OMB), NARA has adjusted its normal operations to balance the need of completing its mission-critical work while also adhering to the recommended social distancing for the safety of NARA staff. As a result of this re-prioritization of activities, you may experience a delay in receiving an initial acknowledgement as well as a substantive response to your reference request from RDT2 or other NARA reference unit. We apologize for this inconvenience and appreciate your understanding and patience.
We also located the publication Appointments and Promotions in the European Theater of Operations: Report of the General Board, U.S. Forces, European Theater, which is available from the U.S. Army Heritage and Education Center. We suggest that you contact them or the U.S. Army Center of Military History for assistance with Army and Army Air Force records. You may wish to contact the Marine Corps History Division and the Navy History and Heritage Command for additional information, too.
We hope this is helpful. Best of luck with your research!