Originally powered by gasoline engines for surface running, it was discovered during her sea trials throughout 1909 and 1910 that these engines were found to be incapable of reaching the submarine's contracted speed and posed a risk of poisoning the ship's crew. U-2 was commissioned in June 1911 and served as a training boat through 1914, though she was mobilized briefly during the Balkan Wars. U-2's design has been described by naval historians as a failure that was rendered obsolete by the time she was commissioned into the Austro-Hungarian Navy.