In 1862-1863 Ewald took an active part in a movement for reform within the Hanoverian Church, and he was a member of the synod which passed the new constitution. He had an important share also in the formation of the "Protestantenverein", or Protestant association, in September 1863. But the chief crisis in his life arose out of the Austro-Prussian War of 1866. His loyalty to King George V of Hanover (son of Ernst August) would not permit him to take the oath of allegiance to the victorious King William I of Prussia, and he was therefore placed on the retired list, though with the full amount of his salary as pension.