Let them both go at it until they devour each other.
Vs.
‘No one can bury heads in sand:’ Hezbollah leader calls for help fighting ISIS in Syria

Calling it a global existential threat, Lebanon’s Hezbollah leader, Hassan Nasrallah, has urged supporters to join the fight against the Islamic State, confirming that his Shiite militant group has been fighting the Sunni extremists all across Syria.
“Today we are facing a kind of danger that is unprecedented in history, which targets humanity itself,”Nasrallah said Sunday during a televised broadcast referring to Islamic State (IS, previously ISIS/ISIL).
“This is not just a threat to the resistance in Lebanon or to the regime in Syria or the government in Iraq or a group in Yemen,” the Shiite movement’s head continued. “This is a danger to everyone. No one should bury their heads in the sand.”
He called on volunteers to stand up against IS extremist fighters: “We invite everyone in Lebanon and the region to take responsibility and confront this danger and end their silence and hesitation and neutrality.”