Complex sentence: Meeting roughly every six months, this task force held its 12th session, focusing on Afghanistan in July, 2015, and will convene the 13th meeting in January, 2016 to discuss US-Russia interactions in Syria and their implications for our bilateral relationship.
Split into simpler sentences: Meeting roughly every six months, this task force held the 12th of these new meetings in July 2015, focusing on Afghanistan. It will convene its 13th meeting in January 2016 to discuss interactions between the two countries in Syria and their implications for our bilateral relationship.