Complex sentence: On the 23 October 2015, Jund al-Aqsa left the Army of Conquest, 17 February 2016,400 + fighters and senior leaders of Jund al-Aqsa merged with al-Nusra Front.
Split into simpler sentences: On the 23 October 2015, Jund al-Aqsa left the Army of Conquest. On 17 February 2016,400 + fighters and senior leaders of Jund al-Aqsa defected to al-Nusra Front.