I'm actually a bit busy on global conf calls at work today, so I'll just add a few data points for FYI sharing and post - no edge/ tone intended. This isn't responding to
@PiperCherokee who has excellent posts - just building on details he shared.
Good points overall but regarding all or nothing, I'll just share each branch offers a full four year and, well, less than full four years of scholarship.
Navy has college programmers who sometimes pick up and receive 3 or less year scholarships after participating. The national scholarship for Navy Option/ Marine option if awarded from HS is 4 years.
Army has 3 or 4 year scholarships awarded from HS - about 25% 4 year and 75% 3 year as of 3 years ago / on average. The 3 year scholarships activate in the second of four years in school.
AF for existing (not this year's new awardees, or future awardees) scholarship winners has a 4 year type 7 to a 3 year type 2 conversion option. so that too is not all or nothing. That 3 year type 2 option kicks in in year 2 of 4. And, the type 2 doesn't always cover all tuition/ fees. Further, a percentage of their winners are unceremoniously dropped after 2 years/ not invited to continue which is definitely the worst outcome after "thinking* and having a scholarship saying you'd won a 4 year type X scholarship but then having bubkis. They also have ICSP where in-college programmers can pick up a scholarship for a portion of their costs.
All branches have college programmers which compete for scholarships and can "pick up" to receive 2 or 3 or reportedly 3.5 year scholarships.
Lastly *some* scholarships and schools offer room and board support/ allow students to keep merit or financial aid moneys- some do not. this can be a big difference. Some ROTC students actually MAKE money and have tuition/ fees/room/ board/ books covered while others have tuition/ fees OR room and board covered and still pay 64k for room and board alone. So which scholarship you choose/ which school you choose can be a big difference.
Depending on your path, say fraternal twin ROTC participants can leave undergrad one with money in teh bank / a surplus, or for the other twin, if year 1 or 2 isn't covered at an expensive school and they pay for room and board they could pay or owe 170k in loans+. Big difference. Hope all of that helps.