The Red Sea port, controlled by the Iran-backed Houthi rebels who hail from northern Yemen, serves as the entry point for 70 percent of the impoverished country's imports as it teeters on the brink of starvation. But it could set off a prolonged street-by-street battle that inflicts heavy casualties. The city is vital for aid shipments, as about 70 percent of Yemen's imports go through its port.
In reality, families in Hudaydah are already starving and desperately relying on humanitarian aid.
Pro-government troops began the assault on Wednesday despite mounting worldwide fears about the humanitarian fallout, pressing toward Hodeida airport south of the city after receiving a "green light" from the coalition. "We thought it could not get any worse, but unfortunately we were wrong".
The Saudi-Emirati coalition's initial battle plan appears to involve a pincer movement.
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 authorised to brief journalists.
Four UAE soldiers were killed during the assault on the port city on Wednesday according to the General Command of UAE's armed forces. Military sources said the deaths were caused by mines and snipers.
The Houthis did not immediately acknowledge the start of the battle.
Forces loyal to Yemen's exiled government and irregular fighters led by Emirati troops had neared Hudaida in recent days.
Exiled President Abed Rabbo Mansour Hadi and many of his advisers now live in Saudi Arabia after Shiite rebels known as Houthis seized the capital, Sanaa, in September 2014. A Saudi-led airstrike in 2015 destroyed cranes at Hudaida.
Aid groups have pulled staff from the town over the deteriorating security situation and warned of catastrophic consequences.
The port remains open, with supplies arriving. According to the Houthis, a pair of missiles struck a landing ship as it was conveying equipment and personnel ashore, leading to the retreat of a flotilla of coalition vessels and a search and rescue operation. Hodeida is the main entry point for food and humanitarian aid for the entire country. The official said UAE intelligence indicated that Houthis had mined the port.
The U.N. International Committee of the Red Cross (ICRC) called on Wednesday for all sides in Yemen's war to protect civilians.
Humanitarian organisations had developed "contingency plans" for the event of an attack affecting the 600,000 people living in and around Hodeida, she said.
The war in Yemen has displaced 2 million more and helped spawn a cholera epidemic.
A draft for a United Nations peace plan for Yemen exclusively seen by Reuters calls on the Houthi movement to give up its ballistic missiles in return for an end to a bombing campaign from a Saudi-led coalition. They have always been restricting imports into Hodeidah to prevent what they say is Iranian traffic of missiles to the Houthis, and say they can swiftly improve food supplies once they control the port.
The global aid group warned of a "high risk of a second outbreak" should water supplies be disrupted.
United Nations refugee chief Filippo Grandi said there was a danger of a more immediate crisis if Yemenis began to abandon their homes in large numbers.
"Today I heard warplanes hovering and the sounds of explosions", a 20-year-old woman, who wished to remain anonymous for fear of reprisal, told Al Jazeera. "This is possibly what we're most concerned about". The UN withdrew its aid workers from Hodeidah on Tuesday even as UN Yemen envoy Martin Griffiths tried to forestall the attack by bringing all parties to the negotiating table. The ship eventually sunk, a major dent in the Saudi- and UAE-planned invasion of al-Hudaydah. "We are in constant contact with all the parties involved to negotiate arrangements for Hodeida that would address political, humanitarian, security concerns of all concerned parties", he said.