What is the good news, written about in a poem, that was brought from Ghent to Aix?

As the poem was written by Robert Browning who dies in 1889 I don't think it was WWI. I found this on a site:-
Some poems work just because they tell such a thumping good story. How They Brought the Good News from Ghent to Aix by Robert Browning is an example.
You don't have to know who the rider, or Joris, or Dirck are. You don't have to know what news was so important to bring to Aix. You don't even have to know where Ghent and Aix are located (although I'm going to tell you in a minute). In fact, Browning admitted that there is "no sort of historical foundation" for this poem. It's still rousing and very fun to read.

You may have a general idea of where Ghent is located. It's a large city of west-central Belgium, about 25 miles north-west of Brussels. Aix is not likely to be on your map now. "Aix la Chappelle" is the modern city of Aachen, Germany. It lies some 70 miles due east of Brussels. Could a horse have galloped the 90 or 95 miles from Ghent to Aix? No way. Does that make the poem any less entertaining? Not at all.
http://www.bl.uk/learning/langlit/poetryperformance/browning/poem2/browning2.html

I am surprised by the accuracy of nearly all of the details used by a foreign poet describing a ride through Flanders.
Joris and Dirck are common Flemish names indeed. Even the horse's names Roos (must be a mare) and Roland are everyday names locally.
The route described by Browning is a perfectly suitable route to ride from Ghent to Aix-la- Chapelle.
Dueffeld must be Duffel (duffel coat!), but the itinerary described by Browning:
Lokeren, Boom, Duffel, Mechelen,Aarschot, Hasselt, Looz ( in Flemish Borgloon), Tongeren..could not be improved by a modern computerprogramme.
Dalhem is halfway between Maastricht and Liège,and an excellent shortcut for Aachen.
So all the details fit, except the major part of the story.What sort of decisions taken at Ghent, events having happened at or near Ghent, could ever have had an impact on Aix?
What news may Browning have imagined when he wrote that it alone " could save her" (= Aachen) "from her fate"?
In Middle Ages Ghent was a town in the County of Flanders,so a dependency of France and never had any say in Aix which was part of the German Empire. Later Ghent was the birthplace of Charles V, but he ruled from Brussels. His Austrian successors did the same.
May be Ghent appealed to Browning because it is where the French King Louis XVIII waited for the outcome of the Battle of Waterloo.
Cannot have been because of the Treaty of Ghent.
No idea how my teachers explained the story, but I do remember that they said it was one of the very rare poems by Browning that were "easily accessible".
For some reason I always wanted to read it as news about the Battle of Waterloo being brought to Germany, but then Browning should have started from
e.g. Brussels. And whether city-gates were still bolted by town-watchs at the time of Waterloo I
don't know for sure.

With all those other details fitting so beautifully, I would have liked the whole story to fit too.

Here's a link to the poem read aloud: https://vimeo.com/73207055

[Links removed and added on November 25, 2016 by shuehorn]