Bruce Catton says “On December 24 [1864] Sherman sent Lincoln a whimsical telegram, offering him the city of Savannah as a Christmas present.”
Had North and South agreed to keep the nationwide system working, or what? How else could he telegraph Savannah to Washington? If the system existed, what were the agreed rules about the two armies using it?
As the Union Army moved south, Telegraph wires were laid.
This and the rapid expansion of the rails were 2 big advantages the North had.
Under Lincoln, the U.S. Military Telegraph Corps were created.
I’m trying to find a cite, but as I recall, over 15,000 miles of Telegraph wires were run.
The United States Military Telegraph Service (USMT) handled some 6.5 million messages during the war and built 15,000 miles of line. In contrast the South used the telegraph in only the most limited fashion.
From here:
Often the telegraph followed the railroad lines. They needed it to control the line anyway.
That is true, but in the case of the Civil War, the Telegraph mainly followed the armies.
And the Union army laid some new rail lines down. And were often able to repair Confederate sabotage of their rail and telegraph lines within hours, while it often took the Confederates days or weeks, if ever, to do the same.
Militaries laying wires were also how military communications happened prior to the development of portable radios. As John Keegan noted, the British term for it - wireless - described its military utility much more succinctly. There’s often a lot of blaming of generalship during WWI for the scale of the bloodbaths, but after the orders were given, there was little that could be done to modify the flow of events. Any attempt to lay wire across no man’s land inevitably resulted in the wire being cut by artillery fire. Wires leading to front line trenched was buried underground to prevent this from happening.
I would guess that this particular telegram was sent by ship from Savannah to Fort Monroe, then on to Lincoln via an actual telegraph line.
That must have been it – Catton says Sherman was incommunicado once he left Atlanta, so he wasn’t laying wire behind him.
At that interview Mr. Brown, who was a shrewd, clever Yankee, told me that a vessel was on the point of starting for Old Point Comfort, and, if she had good weather off Cape Hatteras, would reach Fortress Monroe by Christmas-day, and he suggested that I might make it the occasion of sending a welcome Christmas gift to the President, Mr. Lincoln, who peculiarly enjoyed such pleasantry. I accordingly sat down and wrote on a slip of paper, to be left at the telegraph-office at Fortress Monroe for transmission. . .
They often were but at that point in the campaign the army was advancing so rapidly it often outpaced the ability to lay and protect new wire. At some point, it became faster to take, restore/repair, and operate captured lines.
Separate question. How physically did it work?
Could you send a message from Georgia to Washington in one tap? Was there enough voltage even? Or did they just go from station to station, repeated all the way in a primitive form of “telephone”? (Lincoln: what does this mean, “purple monkey dishwasher”?)
If someone tapped a telegraph line midway, could they ‘listen in’?
Telegraphs were very easy to tap and it happened on both sides.
I don’t know the answer to your first question, but I am quite sure at the time a signal could not go from Georgia to DC.
Interesting question. To establish a timeline, Wikipedia reminds us that Heaviside’s telegrapher’s equations were published in 1876. Which hints that what they had during the U.S. Civil War was comparatively primitive crap that did not work well over long distances, but how far did they go?
Morse’s first line was Washington to Baltimore (40 miles).
I did a little checking, the relays go as far back as the 1830s, which surprised me. They were common and the backbone of the networks by 1844.
So I wonder if the U.S. Military Telegraph Corps were able to set up relays with their miles of wires. In which case, a message could have been sent from Atlanta to DC.
Sure, even if you are limited to 40 miles or 100 miles, all you need to send a message an arbitrary distance are relays.
What I’d wonder more about is how they dealt with multiple users on the same line. What if two operators were trying to send at once? Did every station have a designated, non-overlapping time for them to send?
Dig up a copy of Tom Standage’s wonderful book on telegraphy “The Victorian Internet” - answers this and a bunch of other questions we haven’t thought to ask…
The whole point of Morse’s invention, as he saw it, was that the tape printer provided a written record of the message, and at first any clerks found reading the message by listening to the printer were instantly dismissed.
Repeater stations clean up the signal and retransmit it. At first the clerks would have to do this manually
Boosting the power just boosts the noise as well and if you push it high enough you burn the cable out.
The first transatlantic cable was good for only 1/15 baud, and, yes, Whitehouse fried it by attempting to apply thousands of volts. He was fired.
The problem is dispersion and distortion, which were eventually solved with tricks like loading the cable so as to increase its inductance. Repeaters were not used until 1956.
Multiplexing, eventually
That’s not really analogous to modern multiplexing systems, which can divide up into an arbitrarily-large number of independent messages (at a cost of speed of each of those messages, of course), since that could only do 4: Bidirectional messages were achieved by canceling out the local key at the local clacker, and two message channels each way were achieved by using different polarities on the line. Though of course it’s still four times better than a 1-plex system, and it could enable protocols like having one polarity for routine communications and reserving the other for emergencies or other high-priority communications.