Uh, I think the Americans beat them to the punch on that by more than a few years(and I wouldn't be surprised to learn of some smaller-scale conflicts that may pre-dated the American Civil War where one or both sides made extensive use of rail). The Austro-Prussian War was fought in 1866, while the American Civil War was fought from 1861 to 1865. The Union made extensive use of railroads for troop movements and logistical support from the onset, as well as more than a few artillery pieces that were permanently mounted to rail-cars. Which also wasn't to mention the extensive use of the Telegraph(which normally ran alongside rail lines) by Lincoln throughout the duration of the war.
In fact a number of battles fought in Virginia specifically, as well as elsewhere, were fought specifically over control of rail lines. Getting even more into the historical side of things, part of the reason why Sherman's March to the sea specifically targeted Atlanta was because it was a major Rail Hub for the south and knocking out Atlanta(and their reason for wrapping railroad tracks around trees) did significant damage to the Confederacy's ability to support and supply their Armies further to the north.
Some nations simply took better notes on what the Americans had been doing with the railroads(and the Telegraph) than others did...