@asiegel12, I’ll second @brock.j.young on this one. As I approached BOLC graduation I had the same question in mind, and decided just to type a nice MFR type letter to my Battalion Commander (Senior Rater) thru my Company Commander as an introduction, using the AR 25-50 writing bible as my guide. Their response was, in short, that they certainly didn’t expect that letter but were glad to have received it and were greatly looking forward to meeting me.

The letter of introduction definitely is not a requirement nor is it going to be expected from today’s military leaders, but it sure will go a long way in building rapport within your chain of command and will likely be a nice change from the norm for them. If you’re in a branch where slots and/or jobs are limited, as @logisticus hints at, it may also put you closer to the front of the line for better jobs. Being in Aviation, I was fast-tracked to PL time as opposed to other new LTs and I’d like to think that little things like the letter of introduction made an impact on that.