The Houthis have announced a Red Sea blockade. What does this involve?The Iran-backed Houthis on ​Monday declared a naval blockade against Saudi Arabia, opening a potential new front against the United States in its war with Iran and raising threats to global energy supplies and trade beyond ​the Gulf.Shipping companies have been warned not to load ‌or discharge cargo at Saudi Arabian ports. The Houthi militia said any such activity may result in being targeted “in any location”. ‌Why is the Red Sea so significant?With traffic barely passing through the Strait of Hormuz due to the escalation in fighting between the US and Iran, a closure of the Bab al-Mandeb Strait could be catastrophic for global energy markets.It would remove a critical alternative route for Saudi Arabia to the Strait of Hormuz and intensify fears of energy shortages.Bab el-Mandeb connects the Red Sea with the Gulf of Aden and is a ⁠key route for crude and fuel shipments moving between ​the Middle East, Europe and Asia.What impact will this have on energy prices?Experts say if the Bab al-Mandeb and the Strait of Hormuz are shut simultaneously, about a quarter of the world’s total oil and gas supply would be blocked. Saudi Arabia has so far partly bypassed the Strait of Hormuz by rerouting ships through Red Sea ports, where tankers are filled before sailing through Bab al-Mandab. If that strait is also blocked, the dramatic reduction of fuel supplies could create global economic stress.Ships would be forced to reroute around the southern tip of Africa, sending shipping and insurance costs soaring, exacerbating shortages in energy.“If they really stop ‌and severely hinder those barrels through the ⁠Red Sea, that is going to have an impact on oil prices as well as refined product prices,” John Paisie, president of consultancy Stratas Advisors, told Reuters. “It undermines the whole global economy. At some point, you could have a global recession.”Have the Houthis tried to blockade the Red Sea before?The Houthis previously intervened militarily in 2023 during the Israel-Hamas war in Gaza by threatening and attacking US and Israeli ships in the Red Sea, forcing shipping firms to sail the long way around southern Africa’s the Cape of Good Hope. Red Sea traffic has not fully recovered since these attacks.What is behind the Houthis actions?Houthi military spokesman Yahya Saree said the movement has reacted to a “continued Saudi siege” on Yemeni ports and airports and imposition of land, sea, and air restrictions. The Saudi foreign ministry condemned the blockade and warned that Riyadh “will take all necessary measures to protect its vessels in accordance with international law”. What do the Houthis control?They control about a third of Yemen’s territory, where most of the country’s population lives. They hold the capital, Sanaa, and major cities, including the Red Sea port of Hodeida and Aden on the Gulf of Aden.