Analyzing Islamic State’s military successes and failures thus far, Hillel Frisch notes that after its stunning victories in 2014 over the ill-trained and poorly motivated Iraqi army, IS has had trouble defeating the Syrian and Kurdish militaries, and would likely be at a far greater disadvantage against the IDF. True, there are reasons to fear IS will expand its control in Syria and from there into Lebanon and Jordan, giving it an opportunity to attack Israel. Nevertheless, Frisch concludes, the greater threat to Israel lies elsewhere:
[The significance] of an IS takeover in Syria to Israeli security interests is not so much the IS threat per se, but rather the Iranian reaction to the takeover, and the threat such a reaction would pose to Israel. Israel must meet the Iranian challenge [by establishing] clear red lines, the most important of which is the prevention of the transfer of advanced missile launchers and rockets through both seaports and airports in Lebanon and [a Syrian rump state outside of IS control]. Israel must develop the intelligence capabilities to monitor these facilities, if it has not already done so.
[Furthermore, Israel should] clearly signal to Iran that infringement of these red lines will result in the partial or complete destruction of the installations in question. . . . [It must also establish a] geographical red line in southern Lebanon beyond which an Iranian presence will not be tolerated.
Israel should [likewise] consider an IS assault on Jabal al-Druze, [an area of Syria bordering Jordan and near the Golan Heights] as a red line, automatically initiating a forceful Israeli response. . . . Israel should signal to the organization that it will forcefully oppose any IS attacks or subversion against Jordan [and that] any attack on Israel or Israeli citizens outside Israel, or any attempts to begin operations in Judea and Samaria, will meet with a disproportionate counterattack on IS personnel and infrastructure.
Read more on BESA Center: http://besacenter.org/wp-content/uploads/2016/05/MSPS118.pdf