Among their other achievements, the Prussian military apparently invented wargames. That’s wargames in the tabletop sense: turns, figurines, battles decided by dice, landscapes marked in squares, pen and paper and immensely convoluted rules. Warhammer without the orcs, basically. All this in 1812.
The “Tactical War-game” (Taktisches Kriegsspiel) was the work of a Prussian military advisor by the name of George Leopold von Reiswitz. He constructed the rules, and presented the king with an elaborate cabinet containing the (many) pieces needed to play. It went down well:
the King would usually command one side and Prince von Mecklenburg would command the other…In later life the King claimed that the games played at Potsdam often gave him ideas for the army manoeuvres which took place there.
The King’s interest in the game became well known, and it was as a direct result that the Grand Duke Nicholas of Russia made visits in 1816 and 1817 and became a devotee himself. This lead to a visit to Moscow by Wilhelm in October 1817 during which time they improvised a game on a large scale by chalking out terrain on a number of green topped card tables which were put together.
After a few years the army got really serious about it, issuing a game set to each regiment. Makes sense, given that the alternative to gaming was to march real soldiers around in the mud by their thousands. It was replicated in a few places, and inspired H.G. Wells in the wargame he created a century later. But mostly it fell out of fashion, and seems to have been repeatedly reinvented (rather than copied) over the following 200 years.