Complex sentence: The elections were overseen by the National Elections Commission (NEC) and were the first elections to be run entirely by the country's institutions and security forces since the country's extensive period of civil wars ended in 2003.
Split into simpler sentences: The elections were overseen by the National Elections Commission (NEC). They are the first elections to be run entirely by the country's institutions and security forces since the country's extensive period of civil wars ended in 2003.