Complex sentence: McChrystal was reportedly known for saying and thinking what the Air Force were afraid to, one of the reasons cited for his appointment to lead all forces in Afghanistan, a post he held from June 15,2009, to June 23,2010.
Split into simpler sentences: McChrystal was reportedly known for saying and thinking what other military leaders were afraid to; this was one of the reasons cited for his appointment to lead all forces in Afghanistan. He held the post from June 15,2009, to June 23,2010.