On Tuesday, Yemeni Houthi rebels attacked four cities in southern Saudi Arabia - another episode in the expansion of the six-month-old war in the Middle East, writes The Independent.
The Iran-backed group announced that it was launching a large-scale operation deep into Saudi territory, saying it had struck an air base and energy infrastructure in the country, and released footage of explosions in attacks on trucks near the border.
Later, Houthi-controlled media reported that Saudi warplanes had carried out four air strikes in Yemen's Juba region, east of the capital Sanaa, is in another sign of an escalation that has sent oil prices up 2% to $99 a barrel.
Tensions have been rising for weeks in the Red Sea region, where the Houthis have been attacking Saudi ships in support of Iran, which is maintaining its own blockade of the Strait of Hormuz in an attempt to force the United States to back down.
Analysts say Washington cannot afford to ignore the ongoing problem with the Houthis in the west and that a broader coalition may be needed to finally close the second volatile front in the war with Iran.
Why are the Houthis attacking Saudi Arabia?
The Houthi rebels are a military, political and religious movement that controls most of northwestern Yemen and has disrupted global trade and energy markets by attacking cargo ships and tankers in the Red Sea. sea.
The group made headlines in 2023-2025 for its attacks on shipping in the seaway in support of Hamas in Gaza.
Since then, attacks on Saudi vessels around the Bab el-Mandeb Strait - a key point controlling maritime traffic to the sea - have increased in support of Iran, which is using disruption of commercial shipping as leverage in its war with the US.
Edmund Fitton-Brown, a former British ambassador to Yemen, told The Independent that there was "no doubt" that the group was acting in coordination with Tehran.
Mr Fitton-Brown, who is a senior fellow at the "Foundation for Defense of Democracies" (Foundation for Defense of Democracies), noted that after months of naval attacks, the Houthis "believe that the time has come to test Saudi Arabia's resolve".
"They believe that the Saudis no longer have the will to fight. They believe that the Saudis have shown themselves weak and fearful in the face of the Iranians," he said. "The Houthis believe this is the moment when they can effectively make higher demands and force the Saudis to agree to even more favorable terms than they were willing to accept before".
Saudi Arabia has been fighting the Houthis for years, leading a military intervention against the group since 2015 with the aim of pushing them out of the capital and restoring the government ousted in 2014.
So far, however, they have failed to prevent the group from intimidating commercial shipping passing through the Red Sea.
What do the latest strikes mean for regional stability?
Tuesday's missile and drone strikes were mainly aimed at energy infrastructure in southern Saudi Arabia, but the high number of casualties suggests they are among the the largest attacks on the kingdom since the war began in February.
These attacks are not a new phenomenon, but are part of a wider conflict that has gripped the Middle East, notes Lindsay Newman, an associate fellow at Chatham House.
"The Houthis began attacking tankers passing through the Red Sea after the events of October 7, which led to a drop in traffic of almost 50%, according to available IMF data," she explained to The Independent. "During this period, there has been no sustained recovery in shipping through the Red Sea. The risks in the Red Sea now combine with the vulnerability in the Strait of Hormuz, linked to Iran's strategy to exert pressure on regional actors and the global economy.
Ms. Newman pointed out that one of the main outstanding issues is the resilience of the network of proxy groups (allies acting on behalf of Iran) in the region. While the capacity of Hamas and "Hezbollah" has been weakened, the Houthi military forces "are proving more difficult to contain" despite efforts to stop them.
Crucially, she said, is the fact that this issue was not addressed in the interim agreement between the United States and Iran in June. Before the outbreak of war in February, Washington had insisted on raising the topic of Iran's support for regional proxy groups.
"This week's events make it clear that addressing these proxy groups must be part of any plan to exit the broader regional conflict. Otherwise, these groups can - and likely will - rearm and continue to destabilize the region."
What's next?
Following the Houthi attacks this morning, the Saudi-led coalition fighting the Houthis in Yemen's civil war vowed to "resolutely oppose" the "hostile approach" of the Houthis.
Saudi Foreign Minister Faisal bin Farhan al-Saud condemned the Houthi attacks but insisted that "the path to diplomacy is not closed", even though the Houthis themselves accused the coalition of carrying out strikes on the provinces of Al-Jawf, Al-Bayda, Marib and Taiz.
"Saudi Arabia will always support diplomatic solutions, but the kingdom will never hesitate to defend itself and its interests. We will use all means to fulfill our tasks and obligations.
Ali Shihabi, a Saudi analyst, however, cast doubt on hopes for a diplomatic solution, telling CNN: "Saudi Arabia has realised that the Houthis are not being reasonable and there is very little chance of reaching a political agreement with them."
The risk for the Houthis, according to Mr Fitton-Brown, is that the Saudis "appear to be willing to strike back" after coordinating a naval coalition with Turkey and Pakistan - the so-called "Mecca Joint Defence Agreement" - to counter the Houthis' aggression.
However, Ankara and Islamabad are in no hurry to come to Riyadh's aid, and the kingdom finds itself in conflict with the United Arab Emirates (UAE) at a time when the two countries should be acting unitedly against Iran.
Mr. Fitton-Brown noted that the region expects American leadership to recognize the connection between the different fronts and to intervene where the Saudis have failed to enforce the law of the sea.
"If the Americans ignore the Red Sea and this threat to Saudi Arabia from the Houthis, it would be completely counterproductive," he said.
"Of course, the Americans are unhappy because they did not receive European support for their war against Iran. But in my opinion they have made too little effort to form a coalition dedicated to the implementation of the law of the sea".