Complex sentence: After fifty years, the Noldor defeated Morgoth in the third Battle, called Dagor Aglareb, the Glorious Battle and they went on to besiege Angband for four hundred years.
Split into simpler sentences: After fifty years, the Noldor defeated Morgoth in the third Battle, called Dagor Aglareb, the Glorious Battle. They went on to besiege Angband for four hundred years.