The shock Hamas incursion into Israel was of a scale and sophistication that was previously considered unthinkable.

Hamas attackers came by land, sea and air, overwhelming Israeli defenses, and killing more than 900 people in the country, both troops and citizens.

The level of planning that would have been required for such an assault prompted questions about whether Hamas could have done it alone – and if it had help, whether that could have come from its longtime backer in the region, Iran.

Tehran, which has commended the operation, has denied involvement. Iran’s mission to the United Nations issued a statement calling the attack “fiercely autonomous and unwaveringly aligned with the legitimate interests of the Palestinian people.”

Deputy national security adviser Jon Finer reiterated Monday that the United States believes Iran is “broadly complicit” in Hamas attacks in Israel, but said the US does not have “direct information” linking these attacks to Iran at this time.

“What we can be quite clear about is that Iran is broadly complicit in these attacks for having supporting Hamas going back decades,” Finer said during an appearance on ABC’s “Good Morning America,” pointing to weapons, training and other financial support.

He continued, “What we don’t have is direct information that shows Iranian involvement in ordering or planning of the attacks that took place over the last couple of days. It’s something that we’re going to keep looking at closely.”

Yet Iran’s evolving relationship with Hamas and its Palestinian militant partners, the Islamic Jihad, is well documented. The Palestinian Islamic Jihad – a Gaza-based militant group which is smaller than Hamas but a significant fighting force in the coastal enclave – has enjoyed a long and public alliance with Tehran.

Hamas, on the other hand, has had a more ambiguous relationship with Iran, turning against it for several years over its support for Syria’s dictator President Bashar al-Assad during the country’s civil war. Ultimately it returned to Tehran’s orbit, and has been openly communicating with Iran and its paramilitary allies about its militant goals.

Israel says Iran supports Hamas to the tune of some $100 million dollars a year. The US State Department in 2021 said that the group receives funding, weapons, and training from Iran, as well as some funds that are raised in Gulf Arab countries.

Iran’s paramilitary allies in the region – namely Lebanon’s Shia armed group Hezbollah – have repeatedly boasted about an ironclad security coordination with Palestinian Islamist groups. (Much of the Western world and some Arab countries consider Hezbollah, Hamas and Islamic Jihad to be terrorist groups.)

Kobi Michael, a senior researcher at the Tel Aviv-based Institute for National Security Studies (INSS), says he believes that Iran aims to create “a reality of war in order to exhaust Israeli society, in order to exhaust the Israel Defense Forces.”

“Here is the common denominator between the Iran strategy and the Hamas strategy. Therefore Iran is an asset for Hamas and Hamas is an asset for Iran,” Michael said.

Just over a month before the surprise attack, the deputy head of the Hamas politburo, Saleh Al-Arouri and the Palestinian Islamic Jihad chief Ziad al-Nakhalah were pictured in Beirut alongside Hezbollah Secretary General Hassan Nasrallah.

In April, Hamas’ senior political leader Ismail Haniyeh visited the Lebanese capital for meetings with Nasrallah. How Haniyeh, who is based in the blockaded Gaza Strip, was able to travel to Lebanon is still unclear.

Ismail Haniyeh, center, chairman of the Hamas political bureau, flashes a victory sign, flanked by bodyguards and senior Palestinian officials during a rally at the southern Lebanese port city of Sidon. (Marwan Naamani/picture alliance/Getty Images)

In his recent televised speeches, Nasrallah said that there was no daylight between his group’s strategic goals and those of his Palestinian militant partners. He has also repeatedly alluded to broadening the group’s rules of engagement with Israel to reflect the growing alliance.

Lebanon and Israel are technically in a state of war. Hezbollah has a stronghold in the south of the country which borders Israel. In 2006, an international war broke out between the two countries that led to over 1,100 dead in Lebanon and over 200 dead in Israel.

Since then, exchanges of fire between the warring parties have been extremely rare, with Hezbollah repeatedly threatening to strike Israel with its growing arsenal of missiles and rockets only if Israel were to strike Lebanese territory. Yet in recent months, Nasrallah has changed his tune, vowing to intervene on behalf of the Palestinians in case Israeli troops attacked “Christian and Muslim holy sites in Jerusalem.”

Hezbollah is believed by the US and Israel to possess precision guided missiles. In recent years, Nasrallah has said that his militant group could call upon “100,000 reservists” in a potential war.

An evolving alliance

Hamas and Iran have not always seen eye to eye. The Syrian civil war pitted Assad and his allies, mostly members of the minority Alawite and Shia branch of Islam, against an opposition movement comprised mainly of Sunni Muslims – the dominant Muslim branch. Hamas is a Sunni organization, whereas Iran’s so-called resistance axis is largely Shia.

The rift persisted for several years but began to end as Syria started to normalize relations with powerful Arab countries, such as Saudi Arabia and the United Arab Emirates, in recent years. With the drawdown of the nearly decade-long Shia-Sunni proxy wars that washed over Iraq, Yemen and Syria, Iran’s elite force, the Revolutionary Guards, has since then shifted its focus to Israel.

Tehran’s alliances with Palestinian Islamist actors appear to be a centerpiece of the Revolutionary Guards’ strategy, though the details remain murky.

“The question everyone’s asking is, what role did Iran play? We don’t know,” said Khaled Elgindy, senior fellow at the DC-based Middle East Institute where he directs the program on Palestine and Israeli-Palestinian Affairs. “Iran has clearly been a supporter of Hamas financially, materially and politically. But we don’t know the extent to which Iran was involved in the logistical operational part of this training, or what kind of logistical support (it offered the October 7 operation).”

“I don’t think anyone knows that. Every (country’s) intelligence was caught completely unaware of this, including and especially the Israelis,” Elgindy added.

Whether or not Iran was involved in the operation may have consequences for the future of the war that began on Saturday. If Iran and its Lebanese paramilitary partners helped concoct the plan, then that could portend an expanded involvement by Iran as the conflict carries on.

Yet it is clear that the Palestinian militant-Iranian axis has gone from strength to strength, and that could be enough to put the region on edge. As the war progresses in and around Gaza in the south, where more than 550 Palestinians have been killed by Israel’s bombing campaign, Israel has also reinforced troops on its northern border where Iran’s most powerful partner, Hezbollah, could enter this war to dramatic effect.

As reported by CNN