Iran once boasted that it controlled four Arab capitals: Baghdad, Damascus, Beirut and Sanaa in an alliance dubbed the "Axis of Resistance".
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."
The regional upheavals will depend on the outcome of this war, particularly the collapse or survival of the Iranian regime.