The following is the May 2021 Congressional Budget Office report, The U.S. Military’s Force Structure: A Primer, 2021 Update
From the report
To increase understanding of the choices that the nation faces when considering the defense budget, the Congressional Budget Office has updated its 2016 primer on the structure of the armed forces. This updated version is based on the spending plans and personnel numbers outlined in the Department of Defense’s (DoD’s) Future Years Defense Program for fiscal...
https://news.usni.org/2021/05/21/congressional-budget-office-primer-on-u-s-militarys-force-structure