Danube
The Danube was once a long-standing frontier of the Roman Empire, and today flows through 10 countries, more than any other river in the world. Originating in Germany, the Danube flows southeast for , passing through or bordering Austria, Slovakia, Hungary, Croatia, Serbia, Romania, Bulgaria, Moldova and Ukraine before draining into the Black Sea. Its drainage basin extends into nine more countries. The Danube river basin is home to fish species such as pike, zander, huchen, Wels catfish, burbot and tench. It is also home to a large diversity of carp and sturgeon, as well as salmon and trout. A few species of euryhaline fish, such as European seabass, mullet, and eel, inhabit the Danube delta and the lower portion of the river.
Battle of Neuburg (1800)
The French war goal, to occupy Vienna and force the Habsburgs to accept and comply with peace terms established in 1798, required a double-pronged invasion through northern Italy, which First Consul Napoleon commanded, and through southern Germany, a campaign that fell to Moreau. To secure access into Bavaria and, eventually, to Vienna, the French needed to control the Danube riverway. This was not a new tactic: The stretch of river between Ulm and Neuburg had been the site of major battles of the Thirty Years' War and War of the Spanish Succession. Between Ulm and Ingolstadt, the Danube grows significantly in volume, making it a wide and swift waterway. The Iller joins the Danube at Ulm, dumping massive amounts of water into the stream; at Donauwörth, the Lech enters the Danube. Neuburg, the first significant city on the river after Donauwörth, had been the family seat of the princes of Pfalz-Neuburg; taking it from a princely family of the Holy Roman Empire would be a blow to the morale and prestige of the Habsburgs, whose role it was to protect the small princely domains. Control of the bridges and passages between Ulm and Donauwörth, Neuburg, then Ingolstadt offered an advantage of both transport and prestige.