Complex sentence: In the 19th century it was occupied twice by German troops during the Schleswig Wars but avoided destruction and as the industrial revolution took hold, the city grew to become the second-largest in the country by the 20th century.
Split into simpler sentences: In the 19th century it was occupied twice by German troops during the Schleswig Wars but avoided destruction. As the industrial revolution took hold, the city grew to become the second-largest in the country by the 20th century.