Staunton rooks have six turrets on the top; problematic in that our pieces have 8 sides. So I subdivided the top loop into three segments (two cuts) to give me 24 segments. I used To Sphere to round it out, then lowered every fourth segment.
It’s interesting to see different people’s train of thought. You saw six, so you figured out how to get six. Michael went the easy route with four (only obvious after watching him ). I ended up using Boolean Modifier to get eight.
I used the same technique @David_Roddick mentionned to get 24 round segments, but I went a step further be deleting 3 edges loops on 4 ( keeping 6 edges loops at the end ) then bridge them together to get the nice hexagonal top
After that just a boolean intersect to get 6 crenellations !