12. Was the entire war dominated by trench warfare? Explain

Trench warfare was not an innovation of World War I, but it was never so prevalent in any other war before or since. ... The trench lines had the effect of turning Western Europe into two fortresses whose armies laid siege to each other along a single border. In the east, the geography worked against entrenchment.

Explanation:

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the  seven  days  battles  were  a series of seven battles over seven  days from june 25 to july 1, 1862, near richmond, virginia,  during  the american civil war. the  seven  days ended with mcclellan's army in relative safety next to the james river, having suffered almost 16,000 casualtiesduring  the retreat.