Originally posted by Mr. Ed:

Thanks for all the advice! I can use it. I dug trenches so deep I was taking fall damage in the process of getting in and out of them while working on it. Then I hit ground water and the trenches filled up to where I was swimming and couldn't dig any deeper. The grey thingies and assorted taller gangly creatures attacked. Now I have about a dozen of them trapped in the trench. I can't get a shot off with my bow and they can't hit me with the rocks they toss. Maybe I need to learn how to build a tower so I can shoot down into the trenches better.

The trench doesn't have to be that deep, just deep enough to get vertical walls. Two vikings high should do it. And then you can sprint jump out of it, especially at the corners. Also digging in line with the compass will allow you to get straight walls.