Yemen's Houthi rebels have sent a reminder that their "hands are on the trigger", ready to attack Israel if the Gaza ceasefire ends.
In the lead-up to the deal, the rebels were the only Iran-backed militant group still regularly launching attacks in solidarity with Palestinians in Gaza.
For more than 14 months, they fired at commercial vessels in the Red Sea, and increasingly launched missile and drone strikes towards Israeli territory.
Repeated retaliation from Israel and the United States did little to deter them.
Since the Israel-Hamas ceasefire came into effect on January 19, the rebels have been scaling back their attacks.
As the deal appeared on shaky ground this week, the group vowed to "immediately escalate" if it unravelled.
But even if the ceasefire holds, analysts say the Houthis remain a major threat.
The group have proven to be a "challenge of a different kind" that won't go away easily.
Who are the Houthis?
The Houthis are a Shiite Muslim rebel group that overran Yemen's capital Sana'a in 2014, and have controlled much of the country throughout the ongoing civil war.
The rebels are part of Iran's so-called "Axis of Resistance", along with Hamas in Gaza and Hezbollah in Lebanon.
The network of like-minded militant groups was created to counter United States and Israeli power across the Middle East.
A UN panel report said last year support from Iran and its allies had transformed the Houthis from a local armed group with limited capabilities to a "powerful military organisation".
Sarah Phillips, a professor of global conflict and development at the University of Sydney, said the group's main objective was to control all of Yemen, but they also had an international agenda.
"They are very ideologically aligned and geo-politically aligned with Iran," she told the ABC.
Drama in the Red Sea
The Houthi strikes on Israel and Red Sea commercial ships began shortly after Hamas launched a terrorist attack on Israel on October 7, 2023.
The Hamas attack left about 1,200 Israelis dead, while another 250 were taken hostage to Gaza, according to Israeli authorities.
In response, Israel launched strikes on Gaza that killed an estimated 48,000 Palestinians, and injured hundreds of thousands, according to the Gaza Health Ministry.
Over the past year, the Houthis targeted more than 100 merchant vessels with missiles and drones.
The attacks all but shuttered an Israeli port in the city of Eilat, disrupting cargo and energy shipments that are critical for worldwide trade.
Ships were forced to take a longer, more costly route around Africa to Israel's Mediterranean ports.
[Map of Red Sea]The group was also regularly attacking Israel, managing to strike populated areas in central parts of the country more than 2,000km away.
The Houthis claimed responsibility for a missile strike in Tel Aviv in December that injured at least 14 people.
Although the strikes caused minimal damage, they significantly disrupted civilian life.
Professor Phillips described how the Houthis' attacks played out domestically.
"Within Yemen, and even among people who have hated the Houthis for a very long time, a lot of people said, 'Well, they are doing this good thing by fighting Israel,'" she said.
At the same time, the ongoing civil war in Yemen has killed more than 150,000 people, including fighters and civilians.
It has created one of the world's worst humanitarian disasters, killing tens of thousands more.
Professor Phillips said the Houthis attacks on Israel had helped divert attention from "their very obvious failure to provide Yemenis with the bare essentials for a safe and dignified life".
Houthis de-escalation 'insufficient'
As the Gaza ceasefire took hold, the Houthis announced they would limit their attacks on ships in the Red Sea corridor to only Israeli-affiliated ships.
They also released the 25-member crew of the Galaxy Leader, a commercial ship they seized back in November 2023.
The US said it was "deeply grateful" that the Sultanate of Oman mediated the Galaxy crew hostage release, but cautioned to "not be distracted by this insufficient action by the Houthis".
"Within Yemen, the Houthis continue to round up and detain hundreds of local staff members of the UN, NGOs, and diplomatic missions under abysmal conditions," the White House said in a statement.
The United Nations paused all operations in Yemen's Sa'ada region this week after eight more of its staff were detained by Houthi rebels late last month.
A UN statement said the "extraordinary" decision was made due to the lack of necessary security conditions and guarantees.
The announcement came a day before the UN World Food Programme revealed that a member of its organisation had died in a Yemeni prison after being abducted by the Houthis on January 23.
Since 2021, the Houthis have detained dozens of UN staff. About 24 remain in detention.
'A threat that won't disappear'
Israel, the US and coalition forces struggled to deter the Houthis at the height of their attacks.
Multiple rounds of coordinated air strikes were launched against ports, oil infrastructure, weapons sites and the airport in Sanaa.
But the group did not back down.
Mr Netanyahu said last month the Houthis would "continue to pay a heavy price for their aggression".
This week, as the future of the ceasefire was in doubt, Houthis' leader Abdulmalik al-Houthi warned that the group was "ready to immediately escalate against the Israeli enemy if it returns to escalation in the Gaza Strip".
"Our hands are on the trigger," he said.
Danny Citrinowicz, a research fellow at the Institute for National Security Studies, a Tel Aviv think tank, believes that even with a lasting ceasefire in Gaza, "the genie is out of the bottle".
He described the Houthis as "a challenge of a different kind".
"There's no quick fix … Even if the war in Gaza ends, this is a threat that won't disappear," he said.
"There is no other alternative at the end of the day than to topple them."
Members of Iran's Axis of Resistance have been weakened over the past year.
Israel eliminated top Hamas and Hezbollah leaders in Gaza and Lebanon, and destroyed their military structure.
But experts say the situation with the Houthis is different.
Yemen does not border Israel, so it cannot easily stage a ground invasion as it has in Gaza and Lebanon.
Mr Citrinowicz, who is the former head of the Israeli defence intelligence unit's Iran branch, said they also lacked intelligence on the Houthis.
"That's something that we didn't do because we were focused on more immediate threats," he said.
What could happen next?
When US President Donald Trump was sworn in for a second term, he re-designated the Houthi movement as a "foreign terrorist organisation".
His administration said the US would work with regional partners to eliminate Houthi capabilities and deprive it of resources.
The Australian government listed the Houthis as a terrorist organisation in May last year.
Mr Citrinowicz said Mr Trump's move was a step in the right direction.
But there are fears the designation could have implications for anyone seen as aiding the Houthis.
Charity organisation Oxfam said the move would worsen the suffering of Yemeni civilians, disrupting vital imports of food, medicine, and fuel.
Kamilia Al-Eriani from Melbourne University's school of social and political sciences, said the terrorist status and sanctions were unlikely to affect the Houthis.
She said political negotiations were the best way to address the situation within Yemen, but that would only be possible if the ceasefire holds.
"If not, they will just continue doing what they have done since November 2023."
ABC/Wires
