CNN
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The Middle East is inching closer to an outright regional war as Israel vowed to respond to Iran’s massive barrage of ballistic missiles fired into the country on Tuesday evening, capping a day of dramatic military escalation in the region.

“Iran made a big mistake tonight – and it will pay for it,” Israeli Prime Minister Benjamin Netanyahu said hours after the unprecedented attack.

Iran launched a salvo of about 200 ballistic missiles at Israeli military targets, the largest attack of its kind ever, setting off sirens across Israel and activating the country’s advanced defense systems.

Iran’s leaders said the attack was intended as a warning to Israel not to engage in direct war with its old enemy, and that any Israeli response to the barrage would be met with “stronger and more painful” blows.

The escalation came about 24 hours after Israel launched a ground war in Lebanon to go after Hezbollah, a powerful militant group backed by Iran, and days after Israel killed its leader Hassan Nasrallah in an attack on Beirut.

Here’s what we know.

Tuesday’s attack further changed the dynamics of the conflict, moving from a war involving Iranian allies to a direct confrontation between two regional military superpowers.

It is the second time Iran has launched an airstrike on Israel this year, but Tuesday’s barrage was of a different scale.

In April, Iran launched an unprecedented large-scale drone and missile attack on Israel – the first direct attack on the country from its territory – in retaliation for a suspected Israeli attack on an Iranian diplomatic complex in Syria.

Iran gave 72 hours’ notice for that attack, which was widely seen as aimed at minimizing casualties while maximizing spectacle, with nearly all 300 projectiles knocked out of the sky by Israeli defense systems.

Israel responded a week later with a limited attack on Iran.

This time, Israel learned of the imminent threat just hours before Tehran launched the attacks, with targets including the headquarters of Israel’s Mossad intelligence service, Tel Aviv, Israel’s second-largest city, Nevatim Air Base and Tel Nof Air Base.

Pentagon spokesman Maj. Gen. Pat Ryder said Tuesday’s Iranian barrage was twice as large as the April attack. It also included many more ballistic missiles, which are harder to shoot down and pose a real threat to Israeli civilians – many of whom were evacuated to shelters during the attack.

While the Israeli military said most of the rockets had been intercepted, some landed on Israeli territory and appeared to cause damage. Shockwaves caused by the attack also damaged homes in central Israel, authorities in the country said.

Diplomacy has so far failed to broker an agreement between Israel and Hezbollah, and ceasefire and hostage negotiations between Hamas and Israel have failed.

Even until a few weeks ago, some senior US officials privately believed that Washington had helped successfully thwart a full-scale Iranian attack on Israel through its diplomatic and deterrence efforts, sources told CNN.

“I think Nasrallah was the final straw” for Iran, said Jonathan Panikoff, a former senior intelligence analyst specializing in the region.

With no off-ramp and Israel appearing unwilling to compromise with its regional enemies, Tuesday’s attack is perhaps the clearest sign that a feared regional war is about to ignite.

Meanwhile, both Israel and the US downplayed the effectiveness of the attack. Israel said the attack “failed.”

In nearly a year of war, mounting escalations have repeatedly brought the region to the brink of full-scale conflict.

In recent days, Israel’s ground incursion into southern Lebanon has opened a whole new front and stepped up attacks against other Iranian-backed militants, including launching attacks on the Houthis in Yemen.

Israel has eliminated Hezbollah’s leadership with a series of attacks and massive airstrikes across Lebanon that have attacked the group’s infrastructure and capabilities but also killed more than 1,000 people, displaced around 1 million people and destroyed homes and neighborhoods .

In Gaza, Israel’s war against Hamas continues nearly a year after the Palestinian militant group’s attack on Israel. The ensuing war has killed more than 41,000 people, creating a catastrophic humanitarian crisis and leaving much of the enclave in ruins.

Hamas, Hezbollah and the Houthis are all part of an Iranian-led alliance spanning Yemen, Syria, Gaza and Iraq that has attacked Israel and its allies since the start of the war. They say they will not stop attacking Israel and its allies until a ceasefire is reached in Gaza.

Iran has tried to characterize its attack as a calibrated response to repeated escalations from Israel.

Iran’s Islamic Revolutionary Guard Corps said Tuesday’s rocket attacks targeted Israeli security and military targets and were in response to the Israeli killing of Nasrallah and other commanders, including Hamas political leader Ismail Haniyeh, in the Iranian capital Tehran in July.

Following the assassination of Hamas’ most public figure after attending the inauguration of Iran’s new president, the world held its breath as it waited to see how Tehran would respond.

For months, that response was not forthcoming and tensions appeared to be de-escalating given the dire consequences of all-out war in the Middle East.

But the killings in Israel and the widening war in Lebanon have quickly changed that equation.

On Saturday, Netanyahu delivered a fiery speech targeting Iran, saying that Israel was “changing the balance of power in the region” and that “there is no place in Iran or the Middle East that Israel’s long arm will not reach. ”

Nasrallah’s death was necessary, he said, to return thousands of residents to their homes along the border with Lebanon, displaced by Hezbollah rocket attacks, and to prevent the group from launching a full-scale attack on Israel.

U.S. officials have long believed that both Iran and Hezbollah’s senior leadership want to avoid all-out war with Israel, even though both have exchanged fire.

One major fear for American and Arab diplomats is the possibility that Israel will strike in Iran, possibly against its nuclear facilities. Former Israeli Prime Minister Naftali Bennett urged Israel to take revenge by destroying its nuclear program.

But Iran has made clear that any response from Israel would lead to further escalation. Iranian President Masoud Pezeshkian said the operation was “only part of our power” on Tuesday.

And Hezbollah itself remains a dangerous opponent for Israel, with an arsenal of military assets that the country could deploy.

The US, Israel’s closest ally and largest arms supplier, says it will work with Israel on its response to the attack, with State Department spokesman Matthew Miller promising there will be consequences.

US Navy destroyers have fired interceptors at the Iranian missiles and in recent weeks the US has moved more troops and warships into the region.

Since the start of Israel’s war in Gaza, US forces have also been the target of escalating attacks from Iranian-backed proxy groups. In January, three U.S. Army soldiers were killed and more than 30 soldiers were injured in a drone strike on a small U.S. outpost in Jordan.

During that time, the US has repeatedly stood firm against Israel. Defense Secretary Lloyd Austin said the U.S. will “never hesitate” to protect American forces and interests in the Middle East, and that the U.S. remains prepared and “prepared” to defend its own forces and Israel.