The grisly propaganda video issued by the Islamic State, also known as the Islamic State of Iraq and Syria (ISIS), showing a captured Jordanian air force pilot being burned alive has sparked a popular backlash in Jordan against ISIS.

Like many Americans before 9/11, many Jordanians did not fully appreciate the threat posed by Islamist revolutionary terrorist groups and sought to avoid being drawn into a conflict.  Some Jordanian Islamists even had staged demonstrations inside Jordan in support of ISIS.

ISIS’s indiscriminate violence against Muslims is steadily eroding its appeal in the region. Although young “true believers” from foreign countries continue to answer its siren call to join in a global “holy war,” a growing number of Iraqi and Syrian Sunni Muslims forced to live under its harsh rule are fed up with its ruthless tactics and fanaticism.

The latest video, which is meant to invigorate the zeal of ISIS supporters as well as to humiliate and demoralize its enemies, particularly Jordan’s armed forces, is merely the most recent evidence of a long list of atrocities committed by ISIS.

In addition to decapitating scores of Syrian and Iraqi Sunni Muslims who resisted its rule, ISIS has massacred members of minority ethnic and religious sects, bombed Shiite mosques, kidnapped Christians and seized their property, sold Yazidi women and girls into slavery and used crucifixion as a punishment to intimidate its opponents.

ISIS had sought to use the captured pilot, Lt. Muath al-Kaseasbeh, whose fighter jet crashed in Syria on Dec. 24, as a means of undermining Jordan’s King Abdullah II, a staunch ally of the United States.  ISIS used a Japanese hostage, Kenji Goto, to suggest that Jordan was dragging its feet in a possible prisoner exchange for a jailed female terrorist, Sajida al-Rishawi.

Rishawi was a member of al-Qaeda in Iraq (which later evolved into ISIS) whose suicide vest failed to explode during the Nov. 9, 2005 bombings of three hotels in Amman, Jordan, which killed 60 people. ISIS hoped to drive a wedge between King Abdullah II and Jordanians who opposed his government’s participation in the coalition battling ISIS.  But this plan was foiled by the revelation that Lt. Kaseasbeh already had been executed.

The king cut short a visit to the United States on Tuesday, returning to Jordan to respond to the crisis.  After the announcement of Kaseasbeh’s death, he vowed to fight a “relentless” war against ISIS and ordered the executions of Rishawi and Ziyad Karboli, a senior al-Qaeda prisoner who was convicted of killing a Jordanian in 2008.

Since succeeding his father as king in 1999, Abdullah II has been a firm U.S. ally against Islamist extremism and terrorism.  He took a major personal and political risk to join the high-profile march in France in response to the Charlie Hebdo terrorist attack in January.

Jordan is a key U.S. ally that signed a peace treaty with Israel in 1994 and signed a free trade agreement with Washington in 2001.  It is a reliable partner against ISIS, al-Qaeda, Palestinian extremists and Iran.

The Obama administration has sought to bolster King Abdullah by increasing U.S. aid from $660 million to $1 billion per year between 2015 and 2017.  But it needs to step up its efforts against ISIS to mitigate a major threat to Jordan and the United States as soon as possible.