what is the difference between two verbs 'dig' and 'dig up' in these two sentences?
1. Soon they had dug the ground.
2. soon they had dug up the ground.
They can mean the same.
Note, however, that when we say "The dog dug up a bone", we mean "The dog dug up the ground to get the buried bone". You can't say "The dog dug a bone". (Well, not in this context)