Oh boy... where do I start? There's a lot of things I didn't like about this place, and a lot of it is baked in the culture already, either because people here have only worked here and they don't know any better, or "that's just how things are" in the defense industry.
There is a lot "Factory Worker" mentality here (at least with Software Engineers), you're expected to record your hours by the minute, and by that, I mean that different task/projects get different "charge codes" allocated to them and you're supposed to record and "charge" to those "codes" for every task you do. That leads to some really awkward moments, like meetings that you have to "make up" the time for because there is no charge code associated with them. A lot of people avoid company events because that would mean that you would have to end up making up the time for it (All-hands meetings, different organizations activities, etc). A lot of the mandatory training you'll have to make up in you're own time (although leadership was trying to change this by the time left). Yup, you read that right "MANDATORY TRAINING" on "YOUR OWN TIME", and we're not talking about training that is going to be useful to you in your career as an Engineer, I mean "Ethics" module and what not...
This factory mentality leads to other things like holidays only providing you 8 hours to charge on 9 hour days and you having to make up 1 hour for every holiday.
Work from home, allowed in certain programs, but very discouraged, you'll have to write a direct letter to your supervisor and manager explaining where you're going to "spend those hours". Snowday? Forget it, you can just do mod time or PTO. I even heard they were trying to make people use PTO or make mod time during the COVID-19 crisis. These are things that would be unacceptable in any other company, but here everybody is used to it so everybody dismisses it as "is just the way it is".
My last point, probably the most important one and the reason I left, is that you won't be doing a lot of "Engineering" here. The biggest program here is the "maintenance" stage. Meaning that you'll be going through a big pile of technical debt trying to fix bugs and implement minor functionality. All of these with technology decades old, no tools and vision to fix the root of the problems(IDE? nah we use vim, Version Control? You'll be stuck with Clearcase, etc...). Don't expect to be attending seminars about the latest industry trends and/or best practices, don't even think about doing training outside the corporate modules about the technologies you're currently working with (which again, are at least 15 old).
At the end of the day, if for some reason the program you're working loses funding (common in defense), you'll have a very weak foundation to continue your career in Software, at least outside defense.