A war the world had mostly stopped watching has roared back to life. Since early September, Houthi rebels have pushed south through Yemen's western provinces, seizing the Red Sea port of Mokha and driving tens of thousands of families from towns along the coastal road toward Aden. The United Nations says the collapse of a years-long informal ceasefire has triggered the worst displacement wave in the region in years.

UNICEF said more than 104,000 people, including over 57,000 children, were displaced in just two weeks, with at least nine children killed, twelve injured and three reported missing after an attack on the road linking Yemen's west coast to Aden. Fighting has hit western Taiz, southern Hudaydah and Marib hardest, disrupting 26 UNICEF-supported health facilities and shuttering 243 schools that serve more than 137,000 students.

A separate tally reported by The National puts the total displaced above 125,000 across eight governorates, including Hodeidah, Lahj, Aden, Abyan, Marib, Al Dhalea and Shabwa, with more than 2,000 people making the dangerous sea crossing to Djibouti to escape the fighting.

A strait that moves the world's oil

The stakes go beyond Yemen's borders. Houthi advances have brought the group closer to full control of the Bab al-Mandeb strait, the narrow chokepoint through which a large share of global shipping and energy cargo passes between the Red Sea and the Gulf of Aden. Aid officials warn the fighting is also severing what little remains of Yemen's health and water infrastructure after more than a decade of civil war, with only around 60 percent of health facilities still functioning nationwide.

"They are being blocked and shot at. Right now, they cannot reach us," said Aisha Mohammad, a mother separated from her five children during the evacuation, in an account carried by The National.

International Organization for Migration chief Amy Pope put it starkly, telling reporters that "behind every number is a family who's lost everything." UNICEF's regional director for the Middle East and North Africa, Edouard Beigbeder, said children in Yemen "were already living through one of the world's most grave humanitarian crises" even before this latest escalation, which has pushed the number of Yemeni children needing assistance past 12 million.

Humanitarian agencies have scrambled to respond. UNICEF says it is expanding emergency operations to reach roughly 231,000 people with water, sanitation, health and nutrition support, while the UN's migration agency has allocated emergency funding and is calling for safe humanitarian corridors and protection for aid workers moving through active front lines in Taiz and Hudaydah.

For now there is no sign of a ceasefire. Yemeni government forces, backed by a Saudi-led coalition, are contesting Houthi gains street by street in parts of Taiz, and residents say the front line is shifting daily. Aid groups warn that unless safe corridors are opened soon, the number of displaced, already rising "by the hour" according to UN officials on the ground, will keep climbing through the coming weeks, deepening a crisis the UN has for years called the world's largest humanitarian emergency.