Complex sentence: Serfdom became increasingly rare in most of Western Europe after the Renaissance, but conversely, it grew strong in Central and Eastern Europe, where it had previously been less common (this phenomenon was known as "later serfdom").
Split into simpler sentences: Serfdom became increasingly rare in most of Western Europe after the Renaissance. But, conversely it grew stronger in Central and Eastern Europe, where it had previously been less common (this phenomenon was known as "later serfdom").