Capelle was promoted to "konteradmiral" (rear admiral) in 1906, and to "vizeadmiral" (vice admiral) three years later. In 1912, Capelle was elevated to the nobility, which allowed him to add "von" to his name. He rose to the rank of admiral in 1913, and by 1914, he was Tirpitz's deputy. During the July Crisis that instigated World War I, Capelle was temporarily the acting state secretary, as Tirpitz was away at his summer home. In this capacity, he endorsed the "blank check" Kaiser Wilhelm II had extended to Austria-Hungary in the aftermath of the assassination of Archduke Franz Ferdinand by Serbian terrorists the previous month. With regard to the deepening crisis, Capelle stated that while "many swords will be rattled and much poisonous ink spilled, Europe will not tear itself to pieces over Serbia.