Complex sentence: In March 1810, a revenge attack was undertaken by sailors from five whaling vessels, but their target was Rangihoua Pā, belonging to Chief Te Pahi, the chief who tried to rescue the "Boyd" survivors and then saw them killed.
Split into simpler sentences: In March 1810, a revenge attack was undertaken by sailors from five whaling vessels. Their target was Rangihoua Pā, belonging to Chief Te Pahi, the chief who apparently tried to rescue the "Boyd" survivors and then saw them killed.