ISIS has generally used suicide vests (SVEST) in 2016 due to the ISF’s increasing ability to spot and thwart its vehicle borne improvised explosive devices (VBIED) and suicide VBIEDs (SVBIED). ISIS last executed a VBIED attack on January 11. It since refrained from VBIED and SVBIED attacks in favor of SVESTs due to the ISF’s increasing ability to spot and destroy such attacks.
The resurgence of successful VBIEDs and SVBIEDs attacks suggests the weakening ability of the ISF to adequately and consistently protect the greater Baghdad area. They also show ISIS reverting to its core expertise as a terrorist organization as it loses its capability to project force from its decreasing terrain.
These explosive attacks will play a major factor in the ongoing political dynamics in Baghdad and aggravate already tense relations between the government and protesters if the government fails to guarantee basic security in the city.
Source http://post.understandingwar.org/backgrounder/isiss-explosive-attacks-greater-baghdad-area-april-4-may-11-2016