Complex sentence: Rivalry between the small Border towns is generally played out on the rugby union field and the historical antagonism continues to this day, Hawick's main rival being the similarly-sized town of Galashiels.
Split into simpler sentences: Rivalry between the small Border towns is generally played out on the rugby union field. The historical competition continues to this day, as Hawick's main rival is the similarly-sized town of Galashiels.