Latest reports are that up to 150,000 Saudi troops have massed at the border with Yemen together with heavy artillery. There are a number of allies supporting the Saudis including members of the Gulf Cooperation Council and Egypt.
The Saudis have already carried out bombing attacks. The attacks were against Shia military camps in Sanaa. One attack was on the al-Dalamy air force base adjacent to the civil airport. Rescue workers said at least 15 houses had been destroyed at the civilian compound at the airport. Rescuers had found 25 bodies by Thursday afternoon but said more might be in the rubble. Egypt confirmed that it has a number of troops on transport ships off the Yemen coast who plan to join the invasion.The US confirmed both that it was in contact with the Saudi government and that President Obama has given permission for the Pentagon to provide the Saudis with logistical and intelligence support. General Lloyd Austin, head of US forces in the region, said that the US would aid in keeping the strategic Bab el-Mandeb Strait at the very tip of the Red Sea open to ensure shipments through the Suez canal are not threatened: "We would work in conjunction with our GCC (Gulf Cooperation Council) partners to ensure that those straits remain open."The Saudis struck an air force base near an oil field east of the capital Sanaa, destroying a radar station as air strikes were extended on Friday. The air campaign, that has been code-named "Operation Decisive Storm", is said to be targeting military commands, air defenses, and communications facilities.President Hadi apparently has left Aden, where he was located, and gone to the safety of the Saudi capital Ryadh.The Houthis advanced from their northern stronghold to the south capturing Sanaa last fall.The Houthis are allied with the former president Ali Saleh who still has strong influence in the armed forces. When talks failed to produce a government acceptable to the Houthis, they took control and are setting up their own government.The Houthis are a minority Shia group and it will be difficult for them to gain control of the southern areas where Sunnis predominate. In some areas, Sunni tribes are allying with the Al-Qaeda in the Arabian Peninsula(AQAP) to resist the Houthi advance. The Houthis are supported by Iran but it is not clear how much support they are getting. Many Arab states in the middle east are pursuing a more aggressive policy in the area often with the open or tacit support of the United States:The coalition plans will no doubt receive the blessing of the Arab League at an upcoming meeting. Five of the Gulf Cooperation Council nations have signed on to the military action with Kuwait, UAE, Qatar and Bahrain joining the Saudi operation. However, Oman, Yemen's neighbor to the east has said it will not take part.
The oil-rich Sunni Arab states of the Persian Gulf, longtime U.S. allies, have pursued more assertive foreign policies in recent years, sending troops to crush a pro-democracy uprising in Bahrain and taking part in U.S.-led strikes against Islamic State in Syria. They’re seeking to ward off perceived threats to their absolute monarchies, especially from Shiite groups or from Sunni Islamist movements that seek power via the ballot box, such as the Muslim Brotherhood.The Saudis and others also worry about the increasing influence of Iran in the region.