Put in advance in place that occurred first to last a. Islamic State in Iraq and Syria became a threat b. civil war broke out between ethnic and religious groups c. the United States joins with others to win back Iraq territories from Isis d. Saddam Hussein is removed from power

To arrange the events in chronological order from first to last:

1. d. Saddam Hussein is removed from power (2003)
2. b. Civil war broke out between ethnic and religious groups (after 2003, escalated around 2006-2007)
3. a. Islamic State in Iraq and Syria became a threat (emerged in the late 2000s, particularly gaining power around 2011-2012)
4. c. The United States joins with others to win back Iraq territories from ISIS (2014 onwards)

So the correct order is: d, b, a, c.