When Hamas-led militants streamed over the border into southern Israel on October 7, many feared the terrorist attack would explode into regional conflict.
"Our brothers in the Islamic resistance in Lebanon, Iran, Yemen, Iraq and Syria, this is the day when your resistance unites with your people in Palestine," Hamas' military leader Mohammed Deif decreed, in a siren song to the group's allies abroad.
In the four months since, tensions in the Middle East have bubbled over, with militaries and armed groups from across the region targeting each other's territories.
Data collated by the non-governmental and non-profit Armed Conflict Location & Event Data Project (ACLED) shows a significant escalation in political violence after Israel's war with Hamas broke out.
From the beginning of 2023 up to January 26, 2024, ACLED tracked 30,876 incidents of explosions, armed clashes or violence against civilians in the Middle East. More than half of those happened on or after October 7.
The increase was largely driven by political violence in Israel and Gaza.
Local health authorities estimate more than 26,000 Palestinians have been killed while Israel's government says 1,200 of its citizens were killed in the initial attacks, and a further 210 soldiers have died in fighting since then.
But outside the war in Gaza, the data shows four main hotspots where political violence has been at its highest, and in all those countries Iran-backed groups operate.
A powerful network known as the Axis of Resistance, supported and funded largely by Iran, has embarked on what analysts have described as a "shadow war" in support of Hamas.
As Iran's leader Ayatollah Ali Khamenei publicly claimed the country would not directly intervene in the Israel-Gaza conflict, its proxy forces have given it plausible deniability while ramping up activities to extend their power and influence across the Middle East.
As well as targeting Israeli assets, these groups have aimed their firepower at Western allies in the region.
The US Department of Defense has reported more than 150 attacks on its forces in the Middle East, most recently a drone strike in Jordan that killed three American troops in what could be the deadliest aerial attack on US forces in the region since the Afghanistan withdrawal.
The US has retaliated with strikes in Iraq, Syria and Yemen. ACLED noted this week that there had been at least 61 US air strikes against Axis of Resistance targets in the Middle East since October 7 — compared to just 12 in the previous nine months.
But there are doubts over America's strategy of deterrence in the Middle East and whether it is working effectively.
With domestic pressure mounting on President Joe Biden after the Jordan assault, particularly from Republicans, one option being put forward is for the US to directly strike Iranian targets and its leadership.
University of Sydney Professor Sarah G Phillips, a non-resident fellow at the Sana'a Center for Strategic Studies in Yemen, says both sides are reluctant to directly attack one another.
"I guess from the fact that we haven't seen anything happen yet, [that option is] still part of [the US's] calculations," she said.
"The question is when will it stop becoming a part of the calculations? And I think we're at the point where that could conceivably happen quickly."
Iran is asserting itself in the region
With its web of proxy forces spread across weak and fractured states throughout the region, Iran has long been a focal point for potential escalation in the Israel-Gaza war.
For years, analysts say Iranian-aligned entities have tested weaknesses in US capability in the region and sought to establish a new level of "acceptable" behaviour.
The Israel-Gaza war has provided these groups with a new avenue to extend their power and accelerate their campaign to expel US forces from the region.
Since October, Iran-backed groups in Lebanon, Yemen, Iraq and Syria have used the war to threaten and attack Israel and the US in what appears to be a coordinated campaign to show the strength of Iran's proxy network.
"They call it forward defence. Basically, you've got these groups spread out throughout the region who are able to take different and locally-sensitive initiatives that benefit the overall strategy of Iran," Professor Phillips said.
These actions have raised the stakes of the conflict, adding heat to simmering tensions throughout the region.
"Israel's occupation of Palestinian land has been a major galvanising point and a rallying point for people in the Middle East," says Shahram Akbarzadeh, a non-resident senior fellow at the Middle East Council on Global Affairs in Doha.
"And when there are tensions erupting like this in Gaza or elsewhere in the West Bank, that is bound to be translated into major acts of violence elsewhere in the region."
The instability in the region also comes at a tense time in Tehran, with its leadership under pressure since 2022, when civil unrest and protests broke out over the death of Mahasa Amini in police custody.
More recently, the government has been left reeling by twin bombings at a memorial for assassinated military commander Qassem Soleimani, which killed nearly 100 people and left scores more injured.
The Islamic State group claimed responsibility for what Iran and the UN Security Council have described as a "terrorist attack".
Days after the bombing Iran sent shock waves throughout the region when it launched a surprise cross-border assault on Pakistan's south-west Balochistan province.
Iran claimed it was targeting a Sunni militant group, which has links to the Islamic State group, and followed years of requests for Pakistan to address the presence of militants in the country.
Pakistan quickly followed with a counter-strike on Iranian soil, heightening fears the Middle East turmoil was spreading further, but an Iranian insider claimed the Iran-Pakistan flare-up was driven by efforts to restore internal security and not by its ambitions for the region.
"It does speak to the mentality of the regime in Iran, that they feel under pressure [and] feel they have to do something. They can't be seen as not doing anything about this crisis," Professor Akbarzadeh said.
While the Iranian leadership is grappling with domestic tensions, analysts believe it is also pursuing a key goal to become the dominant force in the Middle East.
"Iran is often quite astutely engaging in domestic political fights that, through these [proxy] groups, help it to gain traction and gain demographic advantage, in some cases, across the region," Professor Phillips said.
"Also having these groups gives [them] an easy passage through Syria, through Lebanon, and into Israel. So it maintains that active threat against Israel."
The new alliance that sprung up in Iraq
Around October 18, a new alliance of Iran-backed armed groups was formed, known as the Islamic Resistance in Iraq (IRI).
It came just a day after the deadly explosion at Gaza's Al Ahli hospital, which Hamas and its allies were quick to blame on Israel, however subsequent analysis has suggested the blast was probably the result of a misfired rocket launched by the Palestinian Islamic Jihad.
According to data from the ACLED project, since the alliance formed it has claimed responsibility for 120 attacks, predominantly drone strikes and shelling on US military facilities in Iraq and Syria.
Analysts have suggested that banding together under one umbrella term allows the militias to show unity against US involvement in the Israel-Gaza war, laying claim to more attacks whilst obscuring the exact groups behind each incident.
On January 20, the IRI claimed responsibility for a barrage of missile and rocket attacks on Al Asad airbase, which hosts American troops.
US Central Command confirmed that several US personnel sustained traumatic brain injuries in the attack.
A few days later, the leader of Kataib Sayyid al Shuhada, one of the groups understood to be aligned with the IRI, announced the second phase of Iraqi resistance in solidarity with Hamas, which he said would include a blockade on Israeli maritime navigation in the Mediterranean Sea.
Since then it has claimed responsibility for further attacks on US sites across Iraq and Syria, as well as inside Israel.
The alliance has claimed strikes on the port of Ashdod, south of Tel Aviv, an Israeli military site in Zevulon. Israel has not confirmed these attacks took place.
The US has carried out several strikes in Iraq since the violence broke out in the region, mainly targeting Hezbollah militias as well as other Iranian-backed groups in what it says is a "direct response" to the escalation in attacks on US targets.
Last week US defence officials confirmed unilateral air strikes against three facilities used by Hezbollah and other militias, understood to have included two in the west near the Syrian border and one south of Baghdad.
ACLED data shows that US-led action in Iraq has killed at least 20 people since October 7.
Following the latest round of US strikes, a spokesman for Iraqi Prime Minister Mohammed Shia al Sudani strongly condemned the "reckless escalation" by US forces.
"This unacceptable act undermines years of co-operation … at a time when the region is already grappling with the danger of expanding conflict, the repercussions of the aggression on Gaza," Major General Yehia Rasool said.
All of this has played out against a backdrop of instability as the Iraqi government negotiates its next step in phasing out the US military presence in the country.
There are about 2,500 US troops stationed in Iraq as part of the coalition formed almost 10 years ago to help the Iraqi government defeat the Islamic State group.
US and Iraqi governments are expected to soon begin talks on the future of the Western coalition in the country, and the recent uptick in violence in the region could be a significant factor.
"The Islamic Resistance in Iraq will likely continue to attack US forces in Iraq and Syria to pressure the [Iraqi government] to order the withdrawal of US forces from Iraq," the Institute for the Study of War (ISW) predicted last week.
Meanwhile, the dwindling Islamic State forces left in the country have continued to engage in armed clashes with Iraqi forces and civilians, while the Turkish military has been fighting against PKK Kurdistan Workers Party in the north of Iraq.
Israel targeting Axis of Resistance in Syria
Syria is a hotspot for hostilities between Israel and Iran and has long been a battlefield where geopolitical rivalries are fought.
The country is regarded as a vital land route for Iran to its Lebanese proxy Hezbollah and other groups in the region, making it a target for Israeli attacks.
"Syria has a major role in the Axis of Resistance, because [it] provides a land bridge," Professor Akbarzadeh said.
Just like in Iraq, Iran-backed groups have similarly targeted US forces and facilities in Syria, most recently the Omar oil field and nearby Conoco mission support site in the east.
Since mid-October, the Pentagon has tallied a total of 83 attacks on US forces in the country.
Golan Heights, an Israeli-occupied territory bordering Syria, has also been the site of increased violence, with Hezbollah and other Iranian-backed militias targeting Israeli settlements in the area.
Islamic Resistance in Iraq has claimed some of these attacks, including launching a drone that crashed in Golan Heights in December.
ACLED data shows Israel's military action in Syria has also ramped up, including repeated strikes on Damascus and Aleppo airports to prevent the smuggling of weapons shipments to Iranian-backed militias.
Israel has also targeted areas where Hezbollah is known to be active and has allegedly struck "military advisors" from Iran's Islamic Revolutionary Guard Corps (IRGC).
In December 2023, Israeli warplanes killed at least eight pro-Iranian and Hezbollah fighters in Syria, as well as a senior IRGC commander.
Most recently, Syria's border with Jordan became another flashpoint after what the US says was an Iran-backed attack on its people at an American outpost.
The one-way drone attack on an American installation known as Tower 22 on January 28 occurred in the north-eastern corner of Jordan.
The small outpost provides a critical logistical hub for US forces in the region, with about 350 army and air force troops stationed in the area.
IRI did not claim direct responsibility for the strike but it did confirm it launched attacks nearby.
The Pentagon says the Jordan attack has all the "footprints" of Iraqi militia Kataib Hezbollah, which the Washington Institute believes likely sits under the umbrella of the IRI.
"Iran likely directed the drone attack into Jordan partly to message to Jordanian leaders the capability and willingness of the Axis of Resistance to escalate," the ISW wrote in its assessment on January 28.
Tensions between Israel and Hezbollah are rising on the border with Lebanon
Since October 7 there has been near daily rocket fire along Israel's border with Lebanon, between Israeli forces and the Axis of Resistance-aligned Hezbollah militant group.
Hezbollah is considered the most powerful and heavily armed group in the Axis of Resistance, boasting tens of thousands of fighters and a sizeable cache of weapons, funded predominantly by Iran.
Analysis by the US-based Center for Strategic and International Studies estimated it has an arsenal of 130,000 rockets, including land attack weapons, and missiles capable of targeting warships and military aircraft.
According to ACLED data, since October 7 Hezbollah has initiated more than 460 attacks on targets in Israel, as well as several inside Lebanon's borders and in neighbouring Syria.
At least six civilians and six Israeli soldiers have been killed in Hezbollah missile, drone and rocket fire.
The IDF has carried out more than 660 air or drone strikes and fired artillery, shells or missiles towards Lebanon more than 1,800 times, according to the same dataset.
More than 200 people have been killed as a result of Israeli military action in Lebanon, predominantly Hezbollah and Hamas militants but also including civilians and journalists.
Israeli authorities have evacuated 200,000 people from 105 border communities since fighting escalated, and the International Organisation for Migration estimates 83,117 people in Lebanon have been displaced.
And following "the most intense exchange of fire" since October 7 over the weekend, Hezbollah appears to be preparing for further escalation in its long-running feud with Israel.
At a funeral procession for Hezbollah fighters killed in Israeli raids, Arab News reported that Hezbollah MP Hassan Ezzedine, who previously served as the group's chief spokesman, addressed the crowd of mourners to underline Hezbollah's ongoing support for Gaza.
"In case of any development that expands this war, the resistance will not stand idly by. It is fully prepared to respond to any folly," he said.
"It will be on the lookout and fight back twice as hard and deal a blow that this enemy could have never anticipated."
Bilal Y Saab, an expert from the Middle East Institute, estimated that if Israel and Hezbollah did enter an all-out war, it could lead to "triple if not quadruple" the number of casualties from the 2006 conflict, which saw 1,200 Lebanese people and 165 Israelis killed during 34 days of fighting.
"Netanyahu, along with the Israeli military, needs a concrete victory against external foes to appease an angry and worried Israeli public. If he cannot achieve it with Hamas, he might try with Hezbollah," he wrote on January 9.
But Professor Phillips says Iran would not want to see Hezbollah get into a conflict "that they can't get out of".
"We've seen skirmishes, but we haven't seen the big, explosion that people are fearing. That may well happen," she said.
"But [Hezbollah] is the ally that is most closely related to Iran and that it would be feeling it really can't afford to lose."
Yemen's Houthi rebels target the Red Sea
More than 2,000 kilometres from where Israeli forces have been carrying out the campaign to destroy Hamas in Gaza, the war has stoked tensions in Yemen.
The country has been in the grips of a civil war for the past eight years since Houthi insurgents took control of the capital city and demanded a new government.
The ensuing violence led to one of the world's largest humanitarian crises, with hundreds of thousands believed to have been killed and at least 21 million in need of urgent assistance as a result of the conflict, according to the UN's Office for the Coordination of Humanitarian Affairs.
The Saudi Arabia-backed government and the Iran-aligned Houthis reached a UN-brokered ceasefire agreement in late 2023, but analysts say recent developments in the Red Sea could scupper those efforts towards peace.
"All of those peace talks have been put on hold now because the dynamic has changed so much [amid the Israel-Gaza war]. And Saudi Arabia cannot be seen to be signing a peace deal with Houthis when the US is exchanging fire with them," Professor Akbarzadeh said.
Days after Israel promised to crush Hamas following the October 7 attacks, Houthi leader Abdul-Malik Badreddine Al-Houthi warned the United States against getting involved in the conflict.
"In the framework of this coordination, there are red lines, a certain scale of events. One of those is a scenario in which the Americans intervene militarily and directly," he said.
"They are providing aid to the Israeli enemy. If they intervene directly, then we are prepared to join the fray, using rocket strikes, UAVs, or any other military option that we can."
From mid-October, around the time other Axis of Resistance groups escalated attacks in the region, Houthis scaled up long-range drone and missile attacks against Israel, most of which were intercepted.
Then on November 19, Houthi fighters hijacked an Israeli-owned, Japanese-operated cargo ship called the Galaxy Leader, taking the ship's crew hostage and declaring that "all ships belonging to the Israeli enemy or that deal with it will become legitimate targets".
Since then it has ramped up attacks on vessels in the southern Red Sea, the busy maritime channel that handles about a quarter of the global container trade.
In early December, the group announced it would target all vessels directed at Israeli ports, including the US-owned Gibraltar Eagle, which was hit by a ballistic missile in mid-January.
The strategy has wrought havoc on global trade. Several major shipping companies have rerouted their vessels to avoid the risk of Houthi attacks, and the longer journeys through southern Africa have sent freight rates skyrocketing.
While the tactic has dealt a blow to Israel's economy, it has also restricted access to critical aid coming into Yemen, sparking concerns over the future of the fragile domestic ceasefire and a resurgence of conflict.
These fears have become even more urgent since US and UK forces — with support from Australia — began responding with air strikes against Houthi targets in Yemen.
Aid organisations operating in Yemen signed a petition on January 16 pleading for all parties to seek resolution via diplomatic channels, rather than through military means.
"Further escalation could result in more organisations being forced to halt their operations … impacts to vital infrastructure, including strategic ports, would have major implications for the entry of essential goods into a country heavily dependent on imports," they wrote.
"All actors have a legal obligation to ensure safe, unimpeded humanitarian assistance so that people in need can access aid services."
With millions in desperate need of aid and a peace deal on hold, the Israel-Gaza war has already had very real consequences for Yemenis.
"At the end of the day, it's the civilian population that ends up paying the highest price," Professor Akbarzadeh said.