They started more war fronts and then tried Ariel attacks.
Explanation:
The trenches were an invention during the time of the first world war when the soldiers began to dig into the fields and fight from them instead of open pitched battle which was common in the time.
The trenches were thus marked as the end of the fast paced war as both forces had defensive portions on the turf.
This was to be worked around by using more war fronts to surround and bypass the trenches as well as ways to mount the other trenches and overtake them.
D. the red area. is the answer.
True ? Hon, What are you asking you need to rephrase this into a question ;)
