WW1 is easy to picture because of the trench warfare but what would a WW2 front line look like? Obviously there are tonnes of different examples with varying answers but let's use the frontline between Germany & The Soviets and later Germany and the Allies in France as an example.
For example I imagine alot of occupied land was just empty fields, how would they control that location?
I don't want to stop anyone else from writing their own answer, but there are several fine answers in this thread here by u/Superplaner and u/RoadRash2TheSequel. I think it'll be worth your while to read through both of the links in u/RoadRash2TheSequel's comment, even if that starts to seem a bit much, because they're very informative, and easier to read than their length suggests.