
The  war against ISIS is taking a dangerous, perhaps inevitable turn. The  terror organization has been keen to expand to southern Syria and the  Syrian capital of Damascus. Now it says it has recruited three Syrian  rebel groups operating in the south of the country in an area bordering  the Israeli occupied Golan Heights — that have switched their loyalties  to ISIS.
 
 This switch means that Israel, the U.S.’s closest ally in the  Middle East, could be threatened from the southwest by the Egyptian ISIS  group of Ansar Bait al-Maqdis in Sinai and by ISIS in southern Syria.
 
 The ISIS war is not going well at all for the US-led alliance in  Syria. ISIS and al-Nusra Front, al-Qaeda’s branch in Syria, are still  the dominant rebel groups in the country. The U.S.-backed Free Syrian  Army is still not a reliable fighting force.
 
 The three rebel groups that just joined ISIS could make that  situation even worse. Two of the groups are small in number, but the  Yarmouk Martyrs Brigade has hundreds of fighters. The Yarmouk Brigades  has been at odds with al-Nusra Front and switched now to join what  leaders of all thrwee groups believe is the future of Islam.
 
 “If Israel was attacked by ISIS, America would expect a  proportionate response by Israel, which is militarily capable of  defending itself,” said Geoffrey Levin, a professor at New York  University. “America would counsel against sustained Israeli involvement  because it could threaten the tacit alliance between America, Iran,  Turkey, and several Arab states against ISIS.”
 
 “More recent reports indicated a closer alliance with [the Islamic  State] due to tensions with JN [al-Nusra Front],” said Jasmine  Opperman, a researcher at Terrorism Research & Analysis Consortium  (TRAC). She said al-Nusra attacked the headquarters of the Yarmouk  Brigade in southern Syria in early December 2014 following clashes  between the two groups.
 
 Al-Yarmuk Martyrs Brigade controlled an area near the  Jordan-Israel border in March 2013. That same month, the brigade took as  hostages some of the United Nations peacekeeping mission soldiers. Even  so, Israel reportedly allowed the brigade to have its wounded fighters  treated in Israeli hospitals.
 
 ISIS has been known for launching surprise attacks and opening new  battlefronts when it seems to be losing. ISIS also has been criticized  by many Arabs and Muslims for not taking its fight to Israel and instead  fighting fellow Arabs and Muslims. An attack aimed at Israel may boost  ISIS’s popularity in the Arab world and refresh its recruitment and  funding efforts.
 
 On the other hand, some of ISIS’s top military commanders were  former officers in Saddam Hussein’s army, and they may resort to what  Saddam did in the 1991 Gulf War when he attacked Israel with mid-range  rockets, hoping to drag the Israelis into a conflict that he was losing.
 
 An Israeli retaliation in 1991 could have jeopardized the U.S-led  coalition that then included Arab countries like Egypt, Syria and Saudi  Arabia. The same is true now.
 
 WHY THIS MATTERS
 
 Despite some recent tensions between the countries, Israel remains  America’s closest ally in the Middle East. Attacks on Israel by ISIS or  affiliated groups could further escalate war in the region, or they  could further strain ties between the Obama administration and the  Israeli government.
 
 “It would be more likely a sign of desperation, as were Saddam's  attempts to lure Israel into the 1991 war as a way of breaking the Arab  coalition against him,” said NYU’s Levin. At that time, continuous  pressure from the first Bush administration and the installation of the  Patriot anti-rocket system convinced the Israelis to refrain from  reacting to Saddam’s attack.
 
 Israel could launch a preemptive attack to destroy or  significantly damage these ISIS-affiliated units whether by air or by  ground forces. Israel used its advanced air force to launch attacks in  Syria several times since the beginning of Syrian civil war in 2011.
 
 Meanwhile, Israel has recently boosted its defenses in the Golan  Heights, saying its main concern was to prevent any major weapon  transfer from Syria to Hezbollah, the Lebanese guerrilla organization  that has engaged in several rounds of war with the Israelis since the  1980s.