That would be a rather large fort. It would be a major base with several hundred men assigned to it.
It would need to be in a very wooded area (that size is going to take a lot of trees) and would be a major trading post.
Normally a fort would be smaller, and buildings would be built outside the fort for trading and storage. The fort would be more for gathering in the case of an attack.
A fort of the size you're describing would need roughly 1,600 logs fifteen feet long and a foot in diameter. This would give you a ten-foot wall buried five feet into the ground. You'd have to dig a ditch five-feet deep about 1,600 feet long, going through all of the roots of the trees. Secondary interior wall would need to be built as well, to cover the gaps in the outside wall. You'd also probably want four blockhouses, one in each corner, to provide fire support along the sides of the walls, as well as a last ditch holdout. Or in other words, a lot more logs to cut. The interior of the fort would need to be stumped, a labor intensive activity. While construction was going on, you'd also need a security force.
Can you justify that amount of work and expense?
Jim Clark-Dawe