The Pentagon has changed all Defense Department references to the Islamic State group from the acronym "ISIL" adopted under former President Barack Obama to the commonly used "ISIS." The change reflects President Donald Trump's long-time insistence that the militant group be called ISIS, not ISIL, according to media reports Friday. 

Pentagon spokesman Capt. Jeff Davis said the military "views ISIS, ISIL and Daesh as interchangeable terms for the same thing." "ISIS is the term most known and understood by the American public, and it is what our leadership uses. This memo simply aligns our terminology," he added.

A Pentagon report dated Feb. 13 addressed to the secretaries of all military departments was titled "Naming Convention of the Islamic State of Iraq and Syria." It referenced a Jan. 28 memorandum by Trump that gave defense officials 30 days to come up with a plan to defeat the jihadist group that controls vast swathes of land in Iraq and Syria. Trump's document referred to the "Islamic State of Iraq and Syria" (ISIS) rather than the Obama-era's preferred use of "Islamic State of Iraq and the Levant," or ISIL. 

In a 2015 tweet, Trump said he wished "Obama would say ISIS, like almost everyone else, rather than ISIL." At another point, Trump became angry with reporter John Heilemann, then of Bloomberg, when the journalist referred to “ISIL.” 

“ISIS,” Trump insisted. “You know, it's one thing with the president — he always says ISIL. ISIL, ISIL, ISIL. Everyone else says ISIS. And it's almost like he does it to bother people, okay? You understand.”

ISIS originated as Al Qaeda in Iraq, initially waging a violent, sectarian campaign against U.S. soldiers and the Shiite community of Iraq in the wake of the U.S.-led 2003 invasion and overthrow of President Saddam Hussein. The group later changed its name to the Islamic State of Iraq before expanding into neighboring Syria to take advantage of the chaos that followed the 2011 rebel uprising against Syrian President Bashar Assad. That is when the naming controversy began in foreign media.

The group's new Arabic-language title in 2013 became "al-Dawla al-Islamiyya fi al-Iraq wa al-Sham" (Daesh). While many foreign media outlets translated this to mean "the Islamic State of Iraq and Syria," the word "al-Sham" technically refers to the entire Levantine region comprising Syria, Palestine, Israel, Jordan, Lebanon and Cyprus. However, a number of local Arabic speakers refer specifically to Syria and especially its capital, Damascus, as "al-Sham."

The evolution continued as the militant organization declared itself a global caliphate in June 2014 and underwent yet another name change. ISIS leader Abu Bakr al-Baghdadi announced the group would be known from then on simply as "al-Dawla al-Islamiyya" or the Islamic State. Since then, many organizations in various languages have qualified this title with such phrases as the "Islamic State group" or "the self-styled Islamic State." A number of Arabic-language outlets partisan to groups active in the fight against the jihadists refused to change the acronym and kept referring to the group as "Daesh." The term, which has become somewhat of a pejorative against the militants, was also picked up by French media.