Complex sentence: The negotiations broke down, however, on the refusal of Denmark to yield the principle of the indissoluble union with the Danish crown; on February 23 the truce was at an end, and on April 3, the war was renewed.
Split into simpler sentences: The negotiations broke down, however, on the refusal of Denmark to yield the principle of the indissoluble union with the Danish crown. On February 23 the truce was at an end, and on April 3, the war was renewed.