Was the machine gun the most revolutionary weapon?

[Southern Senator North Carolina Yankee]

Instant communication had a tremendous impact and it doesn't seem that anyone has mentioned it so far. The fact that you could read about a disaster in the next day's paper by the end of the Victorian Era, when it took weeks to learn about such at the beginning of the Victorian Era, meant that politicals were directly impacted almost in real time by the situation on the front.

Lincoln also kept in the know by spending large amounts of time at the War Department's telegraph office and thus became in a lot of ways the first modern war time President, who had near real time interaction (delay of a few hours maybe) to prod Generals and so forth. A good example of this is at the end of the war when Sheridan messages Grant that "If the thing is pressed, I think it will surrender" and Lincoln intercedes in the exchange with, "Let the thing be pressed". No prior President had that ability and later developments like the radio would improve both intelligence and communication, important aspects with sprawling battlefields with thousands of men that stretched beyond eyesight, even more so when those numbers reached into the millions.