Question

What was it called when both sides fought from behind long ditches they dug with the earth piled in front to protect them?

Answer 1

This is called trench warfare!
The name comes from the trenches, that is the ditches that the soldiers built.

This warfare was typical in the First World War and it led to frequent stalemates: the trenches are easy to defend but hard to attack so for long periods of times the front remained stable.