The American Civil War (1861–1865) was a major conflict with a long string of battles. Has it led to any innovations in 19th-century warfare? It has been pointed out that it may have been the first war to include significant strings of multi-day battles. Did any actual significant inventions occur and if so, were those taken up in later conflicts e.g. on other continents?
For instance, were there any significant special circumstances arising from a long campaign season in the South, from the fact that the conflict split loyalties in some countries, that you had somebody with Lincoln's intellect often meddling with details of the war, or that generals on both sides had been trained in the same pre-war institutions: in terms of an analogy from biology esp. the latter situation — in combination with the contingencies or war and the size of the almost continent-scale conflict — would have provided ample breeding ground for tactical and strategic "cross-over", "mutations", and "progress".
And there was also recent technological change that may have had a special impact. The following pertinent quote is from Stephen Ambrose's Undaunted Courage: Meriwether Lewis, Thomas Jefferson, and the Opening of the American West:
In Jefferson's day, it took six weeks to move information from the Mississippi River to Washington, D.C. In Lincoln's, information moved over the same route by telegraph all but instantaneously. Time and distance, mountains and rivers meant something entirely different to Thomas Jefferson from what they meant to Abraham Lincoln. Rivers dominated Jefferson's thinking about North America.