In early 1881, "Bismarck" went into the "Kaiserliche Werft" (Imperial Shipyard) in Wilhelmshaven for an extensive overhaul of her propulsion system. It was during this refit that her bow torpedo tubes were installed; she also had her original 15 cm guns replaced with more modern quick-firing guns of the same caliber. She went through another round of sea trials from 2 to 13 August 1883, though since June 1882 she had been designated as part of the I. Reserve owing to the tensions related to the Anglo-Egyptian War. By the mid-1880s, the European powers had embarked on the scramble for Africa, and German firms, including Jantzen &amp; Thormählen and the Woermann-Linie, began to press the German government to acquire colonies as well. To this end, the firms attempted to incite attacks from local rulers in West Africa against German traders in the region to try to force the government to place the region under German control. As a result of these incidents, Bismarck, despite his long dislike of overseas colonies, decided to send a squadron to the Bight of Biafra to protect German interests.