that the event was "the first time we attacked live Iranian targets — both facilities and people."

An Israeli F-15 fighter jet Jack Guez | AFP | Getty Images

Iran has issued a threat against Israel following last weekend's attack on an Iranian drone base in Syria. "Tel Aviv will be punished for its aggressive action," Iranian Foreign Ministry spokesman Bahram Ghassemi told local press Monday. "The occupying Zionist regime will, sooner or later, receive an appropriate response to its actions." The strike, which killed seven Iranian military advisors from the country's elite Quds Force in the Syrian city of Homs, has been neither confirmed nor denied by Israel's government. But a senior Israeli official admitted to The New York Times that the event was "the first time we attacked live Iranian targets — both facilities and people." Amid an already chaotic and internecine war involving numerous parties fighting for their own calculated interests, another conflict is coming into focus: the escalation of clashes between Iran and Israel. Since 2013, Israel has carried out more than 100 airstrikes in Syria, primarily targeting the Iranian-funded Lebanese militia group Hezbollah and military convoys. This hasn't featured heavily in news headlines, however, as Israel prefers to act in the shadows to reduce the pressure on adversaries to respond, and because Russia, with whom it has good relations, has so far tolerated its military actions. But the first months of 2018 have seen Israel broaden its intervention to increasingly target its longtime nemesis, Iran, directly.

A shooting war

"The only thing more complex than the Syrian civil war would be the Syrian civil war overlaid with an Israel-Iran shooting war," said Henry Rome, Iran researcher at global risk consultancy Eurasia Group. This would inevitably drag the U.S. further into the conflict in support of Israel, while potentially empowering Russia as a mediator due to its relatively good relations with both sides. Israel and Iran's strategic aims in Syria come into direct conflict with one another. Iran seeks a permanent presence in Syria and Lebanon — part of what regional experts have called the growing "Shia crescent" of influence in the Middle East — as a long-term, strategic objective. And Israel sees an increasing threat in this deepening influence near its borders, which it fears could result in launching posts from which Hezbollah could attack. "There are many Israelis who have felt obliged to plan out a war with Iran, and their political leaders have spoken ominously about that in recent years," former U.S. ambassador to Syria Richard Murphy told CNBC, noting that the threat posed by Hezbollah is "considerable" given the missiles it commands in Lebanon and in supply posts in Syria. Therefore, a major red line for Israel, according to Rome, is the presence of permanent Iranian air, naval, or ground military bases in Syria — hence its strike on the drone base.

Drone wars

The strike came two months after an Israeli F-16 was shot down by Syrian anti-aircraft defenses during an earlier attack on a drone base prompted by an armed Iranian drone entering Israeli airspace in early February. The two Israeli pilots onboard were ejected over Israeli territory and landed in stable condition. This instance underscores just how easily the war could widen, pulling the two adversaries into full-blown conflict over Syria. "Israeli intervention in Syria could easily trigger an escalation of the conflict or a further spillover of violence into the region," Ryan Turner, a senior risk analyst at PGI Group, told CNBC.

Free Syrian Army fighters fire an anti-aircraft weapon in a rebel-held area of Aleppo, Syria December 12, 2016. Abdalrhman Ismail | Reuters