I'm in the process of enlisting as a DEO for AERE, marine systems engineer or naval combat engineer.
I was wondering what the timeline is for promoting through the ranks from Officer Cadet to Captain.
Depends on how fast you get on course realistically. However as an AERE, and most other eng trades you will be captain in 2 years no matter what, and if it takes longer than that you will be backpaid for all the extra time as a captain pay.
Ocdt is 3 months in basic,
2Lt is 8-14 months (14 months for AERE, not sure about the others)
Lt comes after 1 year, or after you are operationally qualified.
Captain is 1 year after that.