Complex sentence: During the early 1900s, the Boulonnais were imported in large numbers to the United States and were quite popular in France; however, the European population suffered severe decreases during 20th-century wars.
Split into simpler sentences: During the early 1900s, the Boulonnais were imported in large numbers to the United States and were quite popular. In France, however, the European population suffered severe decreases during 20th-century wars.