I don’t want to necessarily pawn you over to a YouTube video but there is a really fantastic lecture by Dr. Nicholas Murray on the “The Evolution of Warfare to 1914” that I think addresses this question very well: https://youtu.be/2cbq7iu8FrI

The short answer is “Very Different.” I think Dr. Murray succeeds in answering what for me was one of the more puzzling questions about 1914, which is “why trenches?” The simple answer is that the technical and industrial improvements made between 1870 and 1914, including the invention of barbed wire, a massive increase in the rate and range of fire that a given unit of infantry can produce, improvements in the chemicals and composition of high explosives that vastly increases the destructive power of artillery all contribute to a set of circumstances in which the only relatively “safe” location on the battlefield are traversed, subterranean trenches.

All of that is in stark contrast to the 1860s, 70s, 80s, where even “trench” sieges like the Siege of Petersburg in the American civil war are conducte, technically speaking, with above-ground breastworks.

Some elements of what contributed to this aspect of “the Great War” were understood to a point in 1914. So for example barbed wire, machine guns and long-range rifles were used to devastating effect in the Boer War. But the implications of a full-scale general European conflict between the advanced industrial powers was not especially well understood, except perhaps by a select group of military thinkers who expected any general European war to be a long one.