But the network -- long used as a regional force against Israel -- has been weakened since the Gaza war and now risks collapse, upending the regional balance, analysts said.

"The axis of resistance is over," said Atlantic Council researcher Nicholas Blanford.

Two days after Hamas launched its October 7, 2023 attack on Israel, Prime Minister Benjamin Netanyahu said his country's response would "change the Middle East".

Backed by Israel's powerful ally, the United States, the Israeli leader did not just intend to defeat the Iran-backed Palestinian group, but the entire axis.

The weakening of Lebanon's Hezbollah after its 2024 war with Israel and the fall of Syrian ruler Bashar al-Assad paved the way for Israel to aim directly at Iran.

Since Saturday, the country has been the target of a major US-Israeli offensive, which even killed Iran's supreme leader Ali Khamenei.

Most of the axis's members like Hezbollah, Yemen's Houthis or Iraqi Shiite groups are "trying to understand how to survive", Renad Mansour, senior research fellow at the Chatham House international affairs think-tank, told AFP.

- 'Defensive approach' -

Since deciding to enter the war by launching rockets at Israel on Monday, Hezbollah brought a major Israeli retaliation, which saw bombings across Lebanon and an Israeli ground incursion to create a buffer zone.

"Naim Qassem doesn't want to get involved in this fight," Blanford, who wrote a book on Hezbollah, said, referring to the group's chief.

However, the analyst said Tehran may have forced Qassem to intervene.

Iraq, a longtime battlefield between Washington and Tehran, saw Iran-backed groups claim dozens of drone attacks on US bases, though many were downed.

To Mansour, these groups lack "the necessary military capabilities to inflict significant damage" while the most prominent ones are now "intertwined in the Iraqi state".

The Houthis in Yemen have so far stayed away from the conflict.

"The Houthis are in a calculated holding pattern, or perhaps a defensive approach," said Ahmed Nagi, senior analyst at the International Crisis Group.

However, Nagi believes that while the axis "is facing an existential threat, that does not necessarily mean it will disintegrate".

"The network operates on more than a military level; its political, social and religious ties remain deeply rooted among its groups and are unlikely to unravel because of battlefield setbacks alone."

- 'Turning point' -

The regional upheavals will depend on the outcome of this war, particularly the collapse or survival of the Islamic republic.

For Gulf countries, however, the consequences are already clear.

All wealthy Arab countries on the Gulf were hit by Iranian missiles and drones, while none of these states attacked Tehran.

"If the conflict drags on, it could become a real turning point for the Gulf -- one that reshapes how states think about security, alliances and even their long-term economic futures," Khald Al-Jaber, executive director of the Middle East Council on Global Affairs, said in an op-ed.

Camille Lons, Gulf specialist at the European Council on Foreign Relations, told AFP that "ultimately, they lose on both counts".

"The escalation with Iran shows that the diplomatic rapprochement was not sufficient and all the investment in security with the United States will not have protected them."

Countries that normalised relations with Israel in recent years, like the UAE, found themselves on the front line of Iranian reprisals.

Lons said Gulf countries' ability to influence Washington was also put into question, as "they have been trying for months to avoid a regional escalation and Trump is not listening to them".

Despite costly investments in American military equipment, "very few" are capable of defending themselves on their own, Lons added.

Between mistrust and rivalries, "few options are available to them".