>> that ping times circa 1812 tended to be measured in weeks or months.

Nope. At least, not in France. Their ping times were measured in minutes and hours.

https://www.bbc.com/news/magazine-22909590

"Napoleonic semaphore was the world's first telegraph network, carrying messages across 19h-Century France faster than ever before.[...] At its most extensive, it comprised 534 stations covering more than 5,000km (3,106 miles). Messages sent from Paris could reach the outer fringes of the country in a matter of three or four hours. Before, it had taken despatch riders on horseback a similar number of days."

See also: https://en.wikipedia.org/wiki/Optical_telegraph

"Credit for the first successful optical telegraph goes to the French engineer Claude Chappe and his brothers in 1792, who succeeded in covering France with a network of 556 stations stretching a total distance of 4,800 kilometres (3,000 mi). Le système Chappe was used for military and national communications until the 1850s."

"A symbol sent from Paris took 2 minutes to reach Lille through 22 stations and 9 minutes to reach Lyon through 50 stations."

The original clacks! Terry Pratchett always finds ways to jump up when interesting factoids surface.

Thanks for this tech history lesson, it might explain something about 19th century France that I didn't learn in (French) school.

Yes, the Chappe optical telegraph existed, but it had limitations:

- Use was all but entirely limited to France. On campaign, mesages would revert to horseback.

- It was stopped by inclement weather.

- Net throughput was low, though I don't have a source on message traffic.

- Messages would have been brief ... one might say telegraphic. Little detail could be conveyed.

- Access was limited to government business. At least some of Napoleon's correspondents were likely denied access.

As counsel to others, Napoleon's mail-handling protocol would be subject to the long transits I describe.

>> On campaign, mesages would revert to horseback.

Well, for the army. Naval semaphore (flags) could pass information across serious distance. Scout ships would often be over the horizon from flagships, their messages relayed back in minutes. The speed of pre-electric mechanical communication is underappreciated today.

Also, carrier pigeons were faster than horses.

"Messenger pigeons were used as early as 1150 in Baghdad[8] and also later by Genghis Khan. By 1167 a regular service between Baghdad and Syria had been established by Sultan Nur ad-Din.[9]"

https://en.wikipedia.org/wiki/Homing_pigeon

Fair point on pigeons. Mentioned as an example in Jon Bentley's Programming Pearls, in active use between Mountain View and Santa Cruz as late as the 1970s. Reading the Wikipedia article, I'd not realised use dated back to pharonic Egypt!

Still useful only between (or at least to) given established points, and adding new nodes took time.

Consider that a critical advantage of the Germans over the French in Fall Rot, June, 1940, was radio-equipped tanks, enabling direct unit-to-unit comms and improvisation on the battlefield.

Still, it's sobering that the Royal Road represented the plateau in long-distance information transmission for very nearly 2500 years:

https://en.wikipedia.org/wiki/Royal_Road

I'll also highlight the key phrase tended to be in my original comment.

by the nineteenth century in the UK most mail across the country would be delivered the next day. (im not sure of the history, it could be that in 1812, things were kind of slow, but it quickly sped up!)

A decade or so later into the Victorian age, mail sent in the same city was to be delivered within a couple of hours. In London there there twelve deliveries a day and in smaller cities up to about 6 times a day. People were able to reply and get responses in one day.