JERUSALEM -- Israeli officials remained silent on Thursday about their airstrike in Syrian territory the day before, a tactic that experts said was part of a longstanding strategy to give targeted countries face-saving opportunities to avoid conflict escalation. But Syria's own confirmation of the attack, followed by harsh condemnation not only by Israel's enemies Iran and Hezbollah but also by Russia, may have undercut that effort, analysts said, increasing the likelihood of a cycle of retaliation.
"From the moment they chose to say Israel did something, it means someone has to do something after that," said Giora Eiland, a former head of Israel's National Security Council and a longtime military leader. "Contrary to what I could hope and believe yesterday, that this round of events would end soon, now I am much less confident."
The Iranian deputy foreign minister warned Thursday that Israel's strike would lead to "grave consequences for Tel Aviv," while the Russian Foreign Ministry issued a statement saying that the strike "blatantly violates the United Nations Charter and is unacceptable and unjustified, whatever its motives."
American officials said Israel hit a convoy before dawn on Wednesday that was ferrying sophisticated antiaircraft missiles called SA-17s to Lebanon. The Syrians and their allies said the target was actually a scientific research facility in the Damascus suburbs. It remained unclear Thursday whether there was one strike or two, and what involvement the research outpost might have had in weapons production or storage for Syria or Hezbollah, the militant Lebanese Shiite organization that has long battled with Israel.
Most experts agree that Syria, Hezbollah and Israel each have strong reasons to avoid a new active conflict right now: the Syrian president, Bashar al-Assad, is fighting for his survival in a violent and chaotic civil war; Hezbollah is struggling for political legitimacy at home and battling its label as a terrorist organization internationally; and Israel is trying to keep its head down in an increasingly volatile region.
But it is equally clear that Hezbollah -- backed by Syria and Iran -- wants desperately to upgrade its arsenal in hopes of changing the parameters for any future engagement with the powerful Israeli military, and that Israel is determined to stop it. And Hezbollah is perhaps even more anxious to gird itself for future challenges to its primacy in Lebanon, especially if a Sunni-led revolution triumphs next door in Syria.
Benjamin Netanyahu, the Israeli prime minister, and his deputies said loud and clear in the days leading up to the strike that they saw any transfer of Syria's extensive cache of chemical weapons, or of sophisticated conventional weapons systems, as a "red line" that would prompt action. Now that Israel has followed through on that threat, even without admitting it, analysts expect the country -- perhaps backed by its Western allies -- to similarly target any future convoys attempting the same feat.
"Once this red line has been crossed, it's definitely going to be crossed time and again from now on, especially as the situation of the Assad regime will deteriorate," said Boaz Ganor, head of the International Institute for Counterterrorism at the Interdisciplinary Center in Herzliya, Israel. "They will do the utmost to gain control of those weapons. In that case, I don't see why Israel wouldn't have the same type of calculation that Israel had two days ago into the future."
Mr. Ganor said the United States and Europe should be as concerned as Israel, because Syria's chemical weapons could end up in the hands not just of Hezbollah but of jihadist organizations like Al Qaeda or its proxies. "If one organization will put their hands on this arsenal, then it will change hands in no time and we'll see it all over the world," he said. "We, the international community, are marching into a new era of terrorism."
Eyal Zisser, a historian at Tel Aviv University who specializes in Syria and Lebanon, said that if there was no retaliation to Wednesday's airstrike, "Why not repeat it? For Israel it's going to be the practice." The question, Professor Zisser said, "is what they will try to do next, Syria and Hezbollah, if there is another Israeli attack, whether they will avoid any retaliation the next time as well."
Israel's steadfast silence on the airstrike was reminiscent of its posture after it destroyed a Syrian nuclear reactor in 2007 -- an attack it has never acknowledged, though many officials discuss it with winks and nods. But in that case, President Assad bought into the de-escalation strategy by saying the attack had hit an unused -- and implicitly unimportant -- military building, relieving the pressure for a response.
Syria and Israel are technically at war, though there has long been a wary calm along the decades-old armistice line. Though Wednesday's strike was on Syrian soil, analysts said its actual goal was to send a strong signal to Hezbollah -- something the Lebanese organization tried to deflect in its own statement after the attack, which expressed "solidarity with Syria's leadership, army and people."
"Israel has tried very hard not to take part in all of what happens in Syria, and I don't think we will start to be involved now," said Dan Harel, a former deputy chief of staff of the Israel Defense Forces. "Israel is trying to stay within its own borders, look outside, not be involved -- just trying not to let what happens in Syria change the equation vis-à-vis Lebanon."
The use of either chemical weapons or complex conventional ones like the Russian-made SA-17s would be a game changer in what most here see as an inevitable next war with Hezbollah. Since Israel's bloody war with Lebanon in 2006, Hezbollah is believed to have increased its missile stash to more than 50,000 from perhaps 15,000, including some long-range missiles that can hit any part of Israel. But Israel is well-prepared to defend against even an intense barrage of such rockets. On the other hand, if Hezbollah gained the ability to curtail Israel's relatively free rein in Lebanese airspace, that would truly alter the landscape.
"If they manage to bring down an Israeli plane, it would have two pilots -- for them it's as if they won the war," Yoram Schweitzer, a senior research fellow at Israel's Institute for National Security Studies, said of Hezbollah. "They have the ability to blackmail Israel, to torture the Israeli public opinion. They won't be able to cope with the Israeli Air Force, but just to be able to reduce the free-of-charge Israeli airstrikes, that's the logic."
As experts debated the likelihood of retaliation by Syria, Hezbollah or Iran on Israeli radio and television, residents in the north rushed to get gas masks as municipal workers checked bomb shelters' electricity and security and reviewed emergency procedures. Mayor Nissim Malka of Kiryat Shmona, a town of about 23,000 near the Lebanon border that withstood more than 1,000 rocket attacks in 2006, said his office had been flooded with calls about whether children should go to school, businesses should close and weddings should proceed.
"Every door slamming made people jump," said Mayor Malka, 60. "People are on edge and keep asking if we know anything about what may develop."
Reporting was contributed by Irit Pazner Garshowitz from Jerusalem, Ellen Barry from Moscow, Thomas Erdbrink from Tehran and Anne Barnard from Beirut, Lebanon.
This article originally appeared in The New York Times.