I'm searching for a reasonable timeframe in which a king or courtier of a semi-distant land would be able to receive an extremely urgent message. The world itself is completely different but lets suppose we are trying to make the trip from approximately mainland Denmark to London, England, (but supposing that infrastructure is mostly usable and intact). I will attach a sketch of the actual map, but this comparison is for the sake of scale. (Within the map, our starting location for the messenger is the capital of the southeastern purple kingdom, and the destination is the east coast of the lime green island that is cut off by the bottom margin of the photo). Let's operate under the assumption that we are working with conventional methods of transport available to high medieval civilization (Such as carvels).

Which route would be the fastest realistically? Taking a ship straight from the starting point to the destination, or travelling by road to the port on the southeast of the continent and taking a ship from there. This continent has very powerful easterly currents and winds on the south side, which turn into northerly currents on the east side, and as such vessels sent from the capital would be heavily hampered.

Would there be any other, more efficient method? I'd guess that the only other real method is courier birds, however I imagine that they are not particularly adept at crossing open ocean.

If this is the best method, what range of timeframes would be realistic for the arrival of an extremely urgent message, which is being relayed by multiple different people? (So we can suppose that if our messenger is shipwrecked, someone else will arrive within a similar expected time.enter image description here)

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    $\begingroup$ "Supposing that infrastructure is mostly usable and intact:" what infrastructure? If our infrastructure is "mostly usable and intact" then just send a radio message. If the Roman infrastructure is "mostly usable and intact" then tough luck -- the Romans had no infrastructure whatsoever in Denmark. $\endgroup$ – AlexP Jun 14 '20 at 9:07
  • $\begingroup$ How complex is the message? Enormous speed can be achieved by the use of beacon fires, but that (besides the necessity of maintaining high places with sufficient fuel and men to watch for the beacon before them and maintain the fire, but the message is binary. More complex messaging might be managed by bells on the scale of church bells, with pealing, but that would require a closer network. $\endgroup$ – Mary Jun 14 '20 at 16:32

Here is an equivalent time frame for the Pony Express, in America.

Operated by Central Overland California and Pikes Peak Express Company, the Pony Express was a great financial investment to the U.S. During its 18 months of operation, it reduced the time for messages to travel between the Atlantic and Pacific coasts to about 10 days.

Perhaps a distance of some 2,000 miles.

So if your world has horses, and the ability to establish transfer stations with fresh horses and riders, so the message can be passed from horse team to horse team, this gives a good baseline for the maximum time by land for an established routine message delivery system.

Since your trip seems to be about 500 miles, then interpolated it would seem to be able to be done by land in under three days, perhaps two days and a bit.

As for the sea leg,

The fastest time to row 50 nautical miles – open water (team) is 7 hours 55 minutes 53 seconds by Melikhov Sergey, Shushin Sergey, Salov Igor, Babkov Ivan and Tokar Evgeny, (all Russian Federation) from the port of Trabzon, Turkey to the port of Sochi, Russian Federation, on 21 July 2018.

So how far is it from that yellow island in the lower left to the coast of the lime green nation?


Signal towers. in the classical period, such a network did exist in Greece and Ancient Rome. i heard it said in a YouTube video i watched, that a message could be sent across the whole of the Roman empire in little over an hour by this series of towers.

and the time of the Mongol invasion of China, signal towers informed the emperor of China at the time that China had been invaded by the hordes of Genghis Khan.

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    $\begingroup$ Could you please link to a reputable (or even, semi-reputable) source about those signal towers, whatver they are, which allowed rapid communication of messages across the width of the Roman empire? As in, I don't believe you. (And it is not at all clear whom you call "emperor of China" in the days on Genghis Khan. The best candidate would be the Southern Song emperor, but then the Southen Song state was an ally of the Mongols. Are you confusing Genghis with his grandson Kubilai?) $\endgroup$ – AlexP Jun 14 '20 at 9:14
  • $\begingroup$ @AlexP How about a picture of one? livius.org/articles/place/gheriat-al-garbia-signal-tower $\endgroup$ – Justin Thyme the Second Jun 14 '20 at 14:29
  • $\begingroup$ @JustinThymetheSecond: Yes, the Romans had watch towers, and the guards in those watch towers could send simple signals to the base fort. Many of them. What they didn't have, as far as I know, is a network of communication towers which could transmit messages across the empire. So the request remains: citation very strongly needed for the affirmation that "a message could be sent across the whole of the Roman empire in little over an hour by this series of towers". $\endgroup$ – AlexP Jun 14 '20 at 14:43
  • $\begingroup$ @AlexP Here is a line that basically crossed the entire Germanic-Roman lines, a continuous line of watch towers, forming one continuous network. If it took 30 sec. to process a simple signal per tower, one hour gives 120 'skips', so 20 miles between towers gives a potential of 2,400 miles. It is about 1,000 miles from Rome to London. So yes it is feasible. en.wikipedia.org/wiki/Limes_Germanicus $\endgroup$ – Justin Thyme the Second Jun 14 '20 at 14:57
  • $\begingroup$ @JustinThymetheSecond: Yes, it is feasible. But the first time it was actually done was in the 18th century when Claude Chappe invented the optical telegraph. Lots of things were possible since the dawn of time, but were not actually done until somebody invented a way of doing them. Please find the smallest scrap of source saying that a Roman (or a Greek, or an Egyptian, doesn't matter) had devised a way of transmitting a message (as opposed to a prearranged simple signal) faster than a courier could carry a letter. That's what we call technological progress. $\endgroup$ – AlexP Jun 14 '20 at 15:58

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