The attack on the Red Sea port aimed to drive out Iranian-aligned Shiite rebels known as Houthis, who have held Hodeida since 2015, and break the civil war's long stalemate. But it could set off a prolonged street-by-street battle that inflicts heavy casualties.
The fear is that a protracted fight could force a shutdown of Hodeida's port at a time when a halt in aid risks tipping millions into starvation. Some 70 percent of Yemen's food enters via the port, as well as the bulk of humanitarian aid and fuel supplies. Around two-thirds of the country's population of 27 million relies on aid and 8.4 million are already at risk of starving.
Before dawn Wednesday, convoys of vehicles appeared to be heading toward the rebel-held city as heavy gunfire rang out. The assault, part of an operation dubbed "Golden Victory," began with coalition airstrikes and shelling by naval ships, according to Saudi-owned satellite news channels and state media.
Bombardment was heavy, with one aid official reporting 30 strikes in 30 minutes. "Some civilians are entrapped, others forced from their homes," said Jolien Veldwijk, the acting country director of the aid group CARE International, which works in Hodeida. "We thought it could not get any worse, but unfortunately we were wrong."
The initial battle plan appeared to involve a pincer movement. Some 2,000 troops who crossed the Red Sea from an Emirati naval base in the African nation of Eritrea were awaiting orders to move in from the west after Yemeni government forces seize Hodeida's port, Yemeni security officials said.
Emirati forces with Yemeni government troops moved in from the south near Hodeida's airport, while others sought to cut off Houthi supply lines to the east, the officials said. They spoke on condition of anonymity as they weren't authorized to brief journalists.
Yemen's exiled government "has exhausted all peaceful and political means to remove the Houthi militia from the port of Hodeida," it said in a statement. "Liberation of the port of Hodeida is a milestone in our struggle to regain Yemen from the militias."
Four Emirati soldiers were killed in Wednesday's assault, the United Arab Emirates' state-run news agency said, but gave no details of how they died. The Houthi-run Al Masirah satellite news channel claimed rebel forces hit a Saudi coalition ship near Hodeida with two missiles. The Saudi-led coalition did not immediately acknowledge the incident.
Forces loyal to Yemen's exiled government and fighters led by Emirati troops had neared Hodeida in recent days. The port is some 150 kilometers (90 miles) southwest of Sanaa, Yemen's capital, which has been in Houthi hands since September 2014. The Saudi-led coalition entered the war in March 2015.
The United Nations and other aid groups already had pulled their international staff from Hodeida ahead of the assault. The port remained open, however. Several ships arrived in recent days, including oil tankers, and there was no word from the coalition or the U.N. to stop work, according to a senior port official, who spoke on condition of anonymity because he was not authorized to talk to the media.
Aid groups nevertheless warned of disaster. Robert Mardini, the regional director for the Red Cross, said the push on Hodeida "is likely to exacerbate an already catastrophic humanitarian situation in Yemen."
"The population has already been weakened to extreme levels," he said. David Miliband, the head of the International Rescue Committee, called the offensive "an attack on the political and diplomatic process to bring peace to Yemen." He said the U.N. Security Council must act to secure a cease-fire before the people of Hodeida "suffer the same fate as those in Aleppo, Mosul or Raqqa."
More than 10,000 people have been killed in Yemen's civil war, which has displaced 2 million others and helped spawn a cholera epidemic. Saudi-led airstrikes have killed large numbers of civilians and damaged vital infrastructure.
The U.N. and Western nations say Iran has supplied the Houthis with weapons, from assault rifles to the ballistic missiles they have fired deep into Saudi Arabia, including at the capital, Riyadh. The coalition has blocked most ports, letting supplies into Hodeida in coordination with the U.N. The air campaign and fighting have disrupted other supply lines, causing an economic crisis that makes food too expensive for many to afford.
The U.N. says some 600,000 people live in and around Hodeida, and "as many as 250,000 people may lose everything — even their lives" in the assault. Already, Yemeni security officials said some were fleeing the fighting.
"We hear sounds of explosions. We are concerned about missiles and shells. Some workers have left to their villages for fear of the war," said Mohammed, a Hodeida resident who gave only his first name for fear of reprisals.
The new U.N. envoy to Yemen, Martin Griffiths, tweeted that he was "extremely concerned" by the violence, calling on all parties to exercise restraint. Griffiths' recent appointment as envoy and his push for new negotiations may have encouraged the Saudi-led coalition to strengthen its hand ahead of any peace talks with the Houthis.
Late Wednesday, the Saudi and Emirati governments announced what they called a "multi-faceted plan" to protect civilians in Hodeida, including establishing routes for food, medical supplies and oil shipments from Saudi Arabia's southern city of Jizan and the UAE's capital, Abu Dhabi.
The attack came as Washington was focused on President Donald Trump's summit this week with North Korean leader Kim Jong Un. The U.S. has been supplying targeting information to the Saudi-led coalition, as well as refueling their warplanes, but was not involved in military operations at the port, Pentagon spokesman Maj. Adrian Rankine Galloway said.
"We do not provide any additional support to the Saudi coalition's military operations," he said.
Associated Press writers Ahmed al-Haj in Sanaa, Yemen; Maggie Michael in Aden, Yemen; Samy Magdy in Cairo and Lolita C. Baldor in Washington contributed to this report.
Follow Jon Gambrell on Twitter at https://twitter.com/jongambrellAP . His work can be found at http://apne.ws/2galNpz .