EXPLAINER-What are US troops doing in the Middle East and where are they?

on Iraqi and Syrian targets linked to Iran's Revolutionary Guard and the militias Tehran backs, following an attack on one of the many sites across the Middle East where the U.S. has a military presence. The U.S. has operated bases around the Middle East for decades. At its peak, there were more than 100,000 U.S. troops in Afghanistan in 2011 and over 160,000 personnel in Iraq in 2007.