In Germany, the French Revolution had initially been greeted with awe and enthusiasm. Goethe recognized the beginning of a new era when he witnessed, at the Battle of Valmy (1792), how a ragtag army of volunteers defeated the well-trained war machine of the monarchical allies, carried to victory by the inspirational force of their battle song, the Marseillaise.

In the wars that followed, the Republic's main trump card was a small wiry Corsican artillery officer, Napoleon Bonaparte. He conquered the Italian peninsula for France in a 1796-1797 campaign, and after a less successful campaign in Egypt overthrew the Republic's leading Directorate in a military coup d’état. Named ‘first consul’ (with Sieyès as second consul) Bonaparte resumed the French series of victories after 1800. In battle after battle he defeated variously aligned opponents: Marengo (1800), Ulm and Austerlitz (1805), Jena and Auerstädt (1806), Wagram (1809). And at each turn, the French territory was expanded until it covered all of Western Europe, with Prussia and Austria as helpless client states.

Important French gains had taken place as early as 1797. In a peace treaty with Austria, France traded in some of its Italian conquests (like Venice) for the Viennaruled Southern Netherlands. Indeed, France came to control practically all of the left bank of the Rhine, and Vauban's old dream, to have French territory bordered in the North-East by that natural frontier, came true at last. This was, however, to prove a fatal destabilization for the ancient Holy Roman Empire. Many lordships and fiefs west of the Rhine formed part of the old Empire; they were held by local nobles who constitutionally were vassals of the Emperor at Vienna. That emperor had now, almost literally, sold them down the river, and an arrangement had to be found to compensate them for their losses. When attempts failed to recapture the Rhineland territories, a formal imperial decision was taken (the dishearteningly named Reichsdeputationshauptschluss) in 1803 to reshuffle the fiefs and lordships in the Empire. A number of territories in the imperial heartland (east of the Rhine), which previously had been free lordships immediate under the Imperial crown, were now placed as fiefs and lordships under the dispossessed nobles from the left bank; they lost their immediate status and were, as the terminology had it, ‘mediatized’ – a severe loss of something close to autonomous sovereignty.