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.
"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.
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.
And Israel's military actions are unlikely to abate, as its fundamental aim is to prevent Syria from being used as a base to threaten its interest. "To that end, Israel will continue to target Iranian military infrastructure in Syria and attempt to prevent the transfer of advanced weapons of Hezbollah," Turner added.
Following the Iranian foreign ministry's statement, Hezbollah issued one of its own: Naim Qassesm, the group's deputy secretary-general, announced that Iran would retaliate at a time and place of its choosing.
The next major flashpoint between the two? The Assad regime's fight for the southwestern city of Daraa, some 50 miles from the Israeli border.
"The Israeli military fears the regime will use Hezbollah and Iranian forces to fight the battle and entrench themselves near the city," said Eurasia Group's Rome. He described this as "intolerable" for Israel, which would act militarily to stop the establishment of permanent Iranian positions.
But while escalation is increasing, an all-out war between the two is unlikely, Murphy believes. "I don't think that's on the cards right now. The Iranian goal is to make sure Assad survives."
And so far the Syrian president has done so, with the help of Tehran and Moscow, and is consolidating his power in much of the country.
"It's a game that has its dangers," the ambassador said. "It's intense seeming, but it can be controlled by Tehran and Jerusalem, and I think they would not seek open warfare," Murphy said, adding that Syria itself is in no condition to be in active conflict against Israel.
But each Israeli strike risks retaliation, said Turner, and "that has the potential to trigger a new cycle of escalation and violence that may not be easily contained."