If I get accepted into OCS, but my unit is deploying or considering me as essential personnel, is there a way to delay my OCS start date?

If you are accepted for OCS, the MILPER message will be very clear in describing your status. Once accepted, you are not to be deployed. I know because it happened to me. The Army as a whole needs an Officer more than your unit needs you. Your unit can’t deem you critical or essential; it’s out of their hands at that point.

Even in the peacetime 1990s Marine Corps, it was the same: you’re more valuable to the service as a whole if you get your commission on time and get to the fleet as a new officer, than pretty much any enlisted alternative. My unit said, “We need to send someone here,” or “Who will volunteer for this interesting school?” And after I raised my hand, it was always, “Youre not going to be here long enough for us to get any bank out of you. Denied. Finish OCS, finish college, get your commission, and get out of here. We’ve got 20 more of you we can send, but only one is getting commissioned.” The only way I ever got to pull rank in my favor was getting to qualify on the pistol range while enlisted; my argument was that it’ll prepare me for qualifying as a lieutenant.

I had a more awkward deal. I was selected for OIS, hence was commissioned in a recruiter's office and on AD while still with the unit. So what do they do with an E-4 that shows up wearing a butter bar aboard ship? Turned out I couldn't flop in the old compartment with 31 other sailors. I was too unclean to be put in O 'Country. The CPO community took pity on me and put me up. In return, the new Ensign made them waffles for breakfast. As I was only one of two qualified Electronic Warfare types and the EW shack had one battle chair, I was out of sight and out of mind mostly. Three days later, I had closed out my paperwork and happily left. Skipper and XO were good folk but were just as glad as I was to see me go over the side.