People are not available though. Navies and militaries in all western nations have huge recruiting problems and that's before dropping fertility rates will shrink the entire pool of able bodied potential recruits.
"U.S. Navy Achieves FY25 Recruiting Goal 3 Months Early"
https://www.navy.mil/Press-Office/Press-Releases/display-pre...
Don't believe the what you read about dropping birthdates somehow being a disaster.
The US has always been an immigrant nation and despite the current administration that is still how the military is manned.