At the outbreak of the Austro-Prussian War in mid-1866, Arminius was mobilized along with Prinz Adalbert, the only other Prussian ironclad. The ships were initially based in Kiel, but in the opening days of the war, Arminius raced to Hamburg via the Skagerrak and the Kattegat, a distance of some 940 nautical miles (1,740 km; 1,080 mi), in 100 hours, an impressive feat for an early ironclad warship.[9] Without a naval threat from Austria, the Prussian navy therefore concentrated its effort against the Kingdom of Hanover.