Should I put on weight?

I'm starting the academy in May and will begin field training in September. I'm wondering if I should use this time to focus on gaining weight.

I'm 5'7", 155 lbs, with an athletic build and around 8-10% body fat. I know some people say size isn't everything, but realistically, if my life depended on winning a fight, I'd want to be as prepared as possible. So, how much muscle should I aim to gain, or is it not necessary?

Edit: I should also note it’s city work, so backup isn’t too far away.