Complex sentence: From the 11th century, the Welsh began pushing back the Norman advance and by the end of the 12th century the Marcher lordships were reduced to the the south and south east of the country.
Split into simpler sentences: From the 11th century, the Welsh began pushing back the Norman advance. Nevertheless, by the end of the 12th century the Marcher lordships were reduced to the the south and south east of the country.