In 2017 total U.S. military personnel numbered 2,363,675 with 1,373,650 active and 990,025 in reserve. (DoD photo by Petty Officer 1st Class Daniel N. Woods, U.S. Navy).                                                                                                                                                                                                                                                                                  

https://www.statista.com/statistics/232330/us-military-force-numbers-by-service-branch-and-reserve-component/

Ike on D-Day (Wikimedia Commons)

US MILITARY PERSONNEL (1939-1945)

YearArmyNavyMarinesCoast GuardTotal
1939189,839125,20219,432334,473
1940269,023160,99728,345458,365
19411,462,315284,42754,3591,801,101
19423,075,608640,570142,61356,716*3,915,507
19436,994,4721,741,750308,523151,1679,195,912
19447,994,7502,981,365475,604171,74911,623,468
19458,267,9583,380,817474,68085,78312,209,238

*Coast Guard listed only as wartime strength