The Telegraph was recently developed before the civil war by Andrew Carnegie, so Lincoln employed Carnegie’s technology for military use and made the U.S. Military Telegraph Corps In 1861.
Interesting Fact: “The next year alone, the U.S.M.T.C. trained 1,200 operators, strung 4,000 miles of telegraph wire and sent more than a million messages to and from the battlefield“ (history.com)*
The Telegraph was significant to the civil war because it allowed officers to contact their troops immediately, War strategies could be delivered on the spot, and battlefield reports could be given the day of that battle. Before this technology messages were mainly delivered by horse which could take days, weeks, and even months. The Confederacy was at a loss and the Union had the major advantage of good communication.