Übersetzung - Latein-Englisch - dux iussit milites vallum circa castra fodere

Quite good translation,yedi.
I have only some doubts about vocabulary used here:

castra, -orum --> a camp, encampment (rather not "bivouac" )

and I don't like "the general" here...

dux, ducis (1) a guide, conductor. (2) a leader, ruler, commander.
I would choose here "commander"

My warm greetings!

Ok, commander can be used instead of general in this case.
Maybe bivouac is too modern the word camp is OK.

Not so modern as we simply can't say "soldier bivouac" and the sentence makes reference to "soldier (military) camps", that were used to be set up by Roman Army near to battlefields.

I apologize, jedi. I was wrong. Look:
bivouac definition
I simply haven't met the word in this sens before. So, "bivouac" is ok.

No problem. Since I used a latin-french dictionary first in order to understand the sentence, an then I translated to English.

He,he, it is normal. I also translate everything into Polish (in my mind) and just then into other languages... We think in our mother language. That's natural.