Tribesman from the Popular Resistance Committees, supporting forces loyal to Yemen's Saudi-backed President Abedrabbo Mansour Hadi, in the city of Taez
Riyadh (AFP) - Deadly fighting, a rise in jihadism, the threat of famine -- two years after Saudi Arabia intervened against Iran-backed rebels, Yemen is more unstable than ever.
The chaos has also seen fighting erupt in vital Red Sea shipping lanes, and Riyadh's ally the United States stepping up its involvement.
The war has become "a quagmire", Peter Salisbury, a research fellow at London's Chatham House, said ahead of the March 26 anniversary of the intervention of the Saudi-led coalition.
Yemen itself has fractured to the point where its future "as a functioning unitary state" is hard to imagine, he said.
Financed and equipped by the coalition, various factions are aligned with Yemen's internationally recognised government against the Huthi rebels and their allies.
But analysts warn of tensions among the anti-rebel forces that will likely lead to internal conflict even if the civil war ends, which is unlikely any time soon.
"The entire country continues to fall apart at the seams" while Yemen's elites look out for their own interests, said Adam Baron, a visiting fellow at the European Council on Foreign Relations.
Along with a severe humanitarian crisis, government institutions and overall security have collapsed, leaving ordinary Yemenis the greatest victims, Baron said.
"And unfortunately there's no sign that there is a light at the end of the tunnel."
The United Nations warned this month that Yemen represents "the largest humanitarian crisis in the world."
The conflict has killed nearly 7,700 people, more than half of them civilians, and wounded more 42,500 others, while it has displaced three million people.
Seven ceasefires alongside peace efforts by the UN and former US secretary of state John Kerry failed to stop the fighting.
The Yemen focus of new US President Donald Trump has so far been on a major escalation of attacks against Al-Qaeda in the Arabian Peninsula.
Trump's administration may also see Yemen as a chance to show its resolve against Iran, wrote Joost Hiltermann and April Longley Alley of the International Crisis Group.
Both Washington and Riyadh accuse Tehran of stoking regional unrest, including by arming the Huthis, although Hiltermann and Alley say there has been "very little hard evidence" of such support.
To send a message to Tehran, Washington may seek to increase backing for the Saudi-led coalition but that could prove to be a serious mistake, the two analysts wrote in the journal Foreign Policy last month.
"If Trump rushes headfirst into the Yemeni war, there is a very real risk that the conflict will spiral out of control," they said.
Washington already supplies the coalition with weapons, aerial refuelling and intelligence.
The US military in October suspected Iran played a role in firing missiles towards its warships in the Red Sea, forcing the US Navy to strike back against rebel radar sites.
Trump's administration has accused Shiite-dominated Iran of being the world's biggest state sponsor of terrorism, a view closely aligned with that of Riyadh's Sunni rulers.
- 'A domino effect' -
With Iranian influence to Saudi Arabia's north in Iraq, Syria and Lebanon, Gulf monarchies are acting in self-defence against "strategic Iranian planning to surround the Arabian Peninsula," said Mustafa Alani, a senior adviser to the Gulf Research Centre.
"It's a war of necessity," he said.
Rebel missiles are still fired into Saudi Arabia, and short-range rockets are killing people on the kingdom's southern border despite two years of air strikes.
Rights groups have repeatedly criticised the coalition bombing campaign in Yemen for causing civilian casualties.
Not only have Saudi actions turned a large proportion of Yemenis against the kingdom, perceptions of Saudi military capability "have been considerably diminished," Salisbury says.
But Yemenis, led by Emirati soldiers, have made progress along the Red Sea coast with the aim of seizing the main rebel-controlled port of Hodeida, Alani said.
This would in turn threaten the rebel hold on Taez city and the capital Sanaa.
"We're expecting a domino effect," with Sanaa under pressure in about six months if progress continues, he said.
The aim is not necessarily a military victory but to make the rebels realise they might lose, forcing them back to negotiations where they will make concessions.
Other analysts are sceptical of this strategy.
"These sort of actions... haven't really done much to hurt the Huthis" but add to civilian suffering, Baron said.
Some analysts say the Saudi defence minister, Deputy Crown Prince Mohammed bin Salman, must be seen to win in Yemen to protect his leadership future.
But Alani said Prince Mohammed has taken a lower profile on Yemen over the past year.
"It's become a state war, not a personal war."
Yemen's President Abedrabbo Mansour Hadi, on the other hand, remains prominent even though analysts dismiss him as unpopular and ineffective.
"He's not able to understand that he's not the right man to lead this sort of crisis," Alani said
But with Hadi's "legitimacy" enshrined in a UN Security Council resolution, it would be difficult for the coalition to abandon him "without undermining the entire rationale for entering the war," Baron said.