We spent the entire day altering the terrain of the battlefield.
Out on the prairie we also created some trenches, 10 meters deep, 5 meters wide, and 20 meters long.
While we were at it we disguised some of them to make pitfalls.
Like this they are easy to fill, so we even installed a trebuchet to increase our range.
In addition I crafted a moat and some stone walls along the outside of the river surrounding the fort.
In this way it would be difficult for the enemy to construct a position near the fort.
Even if they assault from the pitfall zone they will find it difficult to advance on the fort.