Complex sentence: In August 1944 the first clashes took place on the Siegfried Line: the section of the line where most fighting took place was the Hürtgenwald area in the Eifel, 20 km (13 miles) southeast of Aachen.
Split into simpler sentences: In August 1944 the first clashes took place on the Siegfried Line. The section of the line then fought over the most was the Hürtgenwald area in the Eifel, 20 km (13 miles) southeast of Aachen.