Evidence that this is the case may be seen in the recently released book Islamic State: Rewriting History by Michael Griffin.
The following words are from a 2004 letter written by the accursed founder of what is now called ISIL, Abu Musad al Zarqawi, while discussing how to wage war against the Shia Muslims of Iraq and how to get the Sunni Muslims of Iraq to hate and fight the Shia Muslims.
Targeting and striking their [the Shia Muslims of Iraq's] religious, political and military symbols will make them show their rage against the Sunnis and bear their inner vengeance. If we succeed in dragging them into a sectarian war, this will awaken the sleepy Sunnis. [Footnote: Abu Musab al-Zarqawi, 'Zarqawi's Cry', National Review, 12 February 2004.] (As quoted in Michael Griffinth, Islamic State: Rewriting History, 2015, Chapter 2.)We must not play into the hands of the ISIL terrorists.