Complex sentence: Several cessions of Danish territory had begun in the 17th century caused a surge of nationalist movements that gained momentum in the 1830s, concluded with a defeat in the 1864 Second Schleswig War, whereafter, a new European outlook was sought, resulting in adjustment and cooperation.
Split into simpler sentences: Several cessions of Danish territory had begun in the 17th century caused a surge of nationalist movements that gained momentum in the 1830s, concluded with a defeat in the 1864 Second Schleswig War. Thereafter, a new European outlook was sought, resulting in adjustment and cooperation.