Complex sentence: Denmark supported France during the Napoleonic wars (1803--1815) and was subsequently excluded from international trade for some years and the loss of Norway in 1814 further caused a large drop in grain exports.
Split into simpler sentences: Denmark supported France during the Napoleonic wars (1803--1815) and was subsequently excluded from international trade for some years. The loss of Norway in 1814 further caused a large drop in grain exports.