Can you be more specific? This might sound counterintuitive, but there is more than one “first impression.” Any phone call, letter, or email you send to your first unit before your arrival is a first impression. How you show up the first day of work (and what day you think is your “first day”) at your Brigade/Battalion is a first impression. Once you get pin-pointed to a Company/Platoon, how you show up for the first day in that formation is another first impression.