Just looking at a map of Germany/France from the 1840’s (all of the hundreds of principalities, duchies, and communes which all disappeared as a result of WWI). And the Fulda Gap— which was a major route to be defended against a potential Soviet wave (tanks, infantry) major Cold War attack, coming from East Germany, in the 1800’s was internal to the German Confederation.
Interestingly the Fulda Gap never featured as a defense position in that Confederation, because any Russian or whatever attack had it reached that far in to Germany would mean the defeat of Germany. The presence of two routes through Fulda and Alsfeld, both cities in Hesse-— is the reason for the power that Hesse retained all through those years and into WWI and II.
Frederick the II, Landgrave of Hesse rented out thousands of the professional soldiers he maintained for just that purpose the mercenary (King owned- important point) Hessians who the British brought to America and whom Gen. Washington defeated completely at the Battle of Trenton on Christmas day. Also- many of the Hessians faded away during the end of the Revolutionary War to remain in the new frontierland (like in North Carolina) who were miners (gold), and there is Mecklenburg (like the German state) county/Charlotte of today. Lot’s of those Hessians stayed around, and joined the many German protestants who had escaped Euro-Monarchists and zero future.
The Fulda Gap, which gave a fairly open route from the Thüringerwald to Frankfurt became significant because of how Germany was divided at the end of WWII and as being the best route for a mechanized force to cut through the US Army in the 3d Armd Div’s portion of the V Corps sector, for the Soviet 8th Guards Army to and over the Rhine River on its way to France. The North German Plain was a similar route for the Soviets to cut the US supply lines based upon Bremerhaven and to get to the NATO depots in Holland and Belgium.
Maps at: https://imgur.com/d1a6tSN
https://www.globalsecurity.org/military/world/war/images/map-de-fulda-gap-6.jpg
https://www.globalsecurity.org/military/world/war/images/map-de-fulda-gap-3.jpg
https://www.globalsecurity.org/military/world/war/images/map-de-fulda-gap-5.jpg
