Complex sentence: In theory, that was a promotion as Russia was one of Prussia's two most powerful neighbors, but Bismarck was sidelined from events in Germany and watched impotently as France drove Austria out of Lombardy during the Italian War of 1859.
Split into simpler sentences: In theory, this was a promotion, as Russia was one of Prussia's two most powerful neighbors. But Bismarck was sidelined from events in Germany and watched impotently as France drove Austria out of Lombardy during the Italian War of 1859.