Complex sentence: The 1st Battalion of the 1st Guards Brigade first reached the VRS positions at Gradina Hill, which quickly overrun and the battalion proceeded towards Jasenica, about north-east of Cavtat, reaching the village by the afternoon.
Split into simpler sentences: The 1st Battalion of the 1st Guards Brigade first reached the VRS positions at the Gradina Hill. Those were quickly overran and the battalion proceeded towards Jasenica, about to the northeast of Cavtat, reaching the village by the afternoon.