When Israel and the United States conducted an intensive bombing campaign in Iran last year, Tehran's regional network of armed proxies and partners largely stood on the sidelines.
But the so-called axis of resistance is expected to enter the fray and back Iran if US President Donald Trump follows through on his threats and authorizes military action against the Islamic republic, experts say.
Iran views a potential conflict with the United States as an existential threat, unlike the war in June, said Hamidreza Azizi, a fellow at the German Institute for International and Security Affairs.
That means Tehran is "ready to go all in and use whatever capacity it has, in terms of its own military capabilities, and at the same time the asymmetric capacity of the axis of resistance" to ensure its survival, said Azizi.
There are already signs that Iran's allies in Iraq, Lebanon, and Yemen are preparing for war in the event of a US attack on Tehran.
Weakened Allies
Iran has spent decades building the axis, a sprawling but loose-knit network of armed proxies and Tehran-backed militant groups in the Middle East. Members include Lebanon's Hezbollah, Yemen's Huthi rebels, and pro-Iranian militias in Iraq.
The network has been a key element of Tehran's strategy of deterrence against perceived threats from the United States and, primarily, Israel.
But the alliance has suffered a series of major blows in recent years. The government of Syrian President Bashar al-Assad, the only state actor in the network besides Iran, was toppled in December 2024.
SEE ALSO: One Year After Assad's Fall: Iran's Strategic Collapse In SyriaHezbollah, meanwhile, has been severely weakened after a bruising yearlong war with Israel, which killed the group's longtime leader Hassan Nasrallah.
Still, despite its diminished fighting capabilities, the network can provide additional firepower to Iran in the event of a conflict with the United States, experts say.
Pulling The Trigger
During the 12-day war with Iran in June, Israel and later the United States bombed key Iranian nuclear and military sites. Tehran responded by firing hundreds of ballistic missiles and drones at Israel, its archenemy, and targeting a US base in Qatar.
Members of Iran's axis of resistance did not get involved in the brief conflict.
"Iran didn't pull the trigger during the June war," said Azizi. "Iran at the time concluded that it could manage the conflict on its own. It didn't want to expand the conflict and wanted to end it as soon as possible."
But a possible new conflict with the United States would change Iran's calculations, say experts.
Iran's clerical establishment is at its weakest point in decades, facing unprecedented unrest and an economic collapse at home and a massive US military buildup on its doorstep. Fighting for its survival, Iran's rulers are willing to use all the tools in its arsenal, experts say.
SEE ALSO: Hatam Qaderi: Iran's Leaders Praying For A 'Miracle' As Grip On Power Erodes'All Bets Are Off'
"We are already seeing signs of the axis of resistance -- what's left of it -- being activated," said Azizi.
The leader of Hezbollah said on January 26 that the group was preparing for "possible aggression and is determined to defend" itself but did not say how he would act if Iran was attacked.
Hezbollah, which has long been Iran's most potent proxy, remains a formidable threat, experts say.
"Hezbollah is down but not out," said Sascha Bruchmann, a military and security affairs analyst at the London-based International Institute for Strategic Studies. "It has lost much of its strategic capabilities, much of its missile arsenal, UAV manufacturing workshops, and the attack tunnels along the border with Israel, but it remains a potent militia."
In neighboring Iraq, pro-Iranian militias have launched a recruitment drive for fighters, including suicide bombers.
The leader of Kataib Hezbollah, one of the militias, issued a fiery statement on January 25, calling on his fighters to be prepared for war.
Established in 2007, Kataib Hezbollah is one of the most powerful members of the Popular Mobilization Forces (PMF), an umbrella organization of mostly Shi'a, Iran-backed armed groups that has been a part of the Iraqi Army since 2016. The PMF is a major military and political player in Iraq.
"Drawing Iraq into this conflict might cost them politically," said Bruchmann. "But all bets are off if [Iran's Supreme Leader Ayatollah Ali] Khamenei is killed or the regime might believe it is falling as some of the Iraqi Shi'a militias have sworn loyalty to Khamenei."
In Yemen, the Huthi rebels have threatened to withdraw from a cease-fire deal reached with the United States last year. The Huthis agreed to halt their missile and drone attacks on international shipping in the Red Sea. In exchange, the United States pledged to stop air strikes targeting the group.
Colin Clarke, executive director of the Soufan Center, a New York-based think tank, said if the axis remained silent again after another assault against Iran it could "risk losing relevance."
"These proxies were designed as a tripwire for the regime, so using them in times of crisis would seem essential," he said.