The Saudi Arabian air force, along with a half dozen other Sunni allies in the Gulf, bombed targets in Yemen yesterday, challenging the Iranian-backed Shia Houthi tribesmen who have been trying to overthrow the Sunni government.

Planes from the United Arab Emirates, Qatar, Bahrain, Kuwait, Jordan, Morocco, and Sudan are taking part in the operation, while Egypt, Jordan, Sudan, and Pakistan were readying ground forces to invade.

The U.S. supports the Saudi attack and hs offered "intelligence and logistical support."

Reuters:

A Saudi official familiar with defense matters told Reuters that a "land offensive might be needed to restore order."

Meanwhile, Iran's Foreign Ministry on Tuesday demanded an immediate halt to the "aggression and air strikes" in Yemen, the semi-official Fars news agency reported on Thursday.

"Military actions in Yemen, which faces a domestic crisis ... will further complicate the situation," Fars quoted Foreign Ministry spokeswoman Marzieh Afkham as saying.

A United Arab Emirates official expressed Gulf Arab concerns about Iranian influence in Yemen.

"The strategic change in the region benefits Iran and we cannot be silent about the fact that the Houthis carry their banner," UAE Minister of State for Foreign Affairs Anwar Mohammed Gargash wrote on Twitter.

The other Arab countries along with Pakistan reported to be willing to take part in the operation are also mostly Sunni.

Saud al-Sarhan, director of research at King Faisal Center for Research and Islamic Studies in Riyadh: “It is a clear message on the ‘Saudi defense doctrine’. Security and stability in the Arabian Peninsula is a red line, and Saudi Arabia doesn’t tolerate any attempt to destabilize the region."

Yemen's slide towards civil war has made it a crucial front in Saudi Arabia's rivalry with Tehran, which Riyadh accuses of stirring up sectarian strife throughout the region and in Yemen with its support for the Houthis. Iran publicly denies funding and training the Houthis.

Fighting has spread across Yemen since last September, when the Houthis seized Sanaa and began to fan out across the country, forcing Hadi out of the capital.

Ambassador Jubeir said the assaults had been launched in response to a direct request by Hadi, who supported Washington's campaign of drone strikes against al Qaeda's Yemen branch.

This is the Saudis' first overt move to counter Iranian influence in the region, which has been spreading in recent years thanks to the U.S. enabling Iranian hegemony.  The Saudis appear to be calling in a lot of chits, especally with Egypt and Pakistan, in order to unite the Sunnis.  If they go ahead with a ground operation against the Houthis, there will be a risk that Iran sends in its own forces, opening up the chasm of a region-wide religious war.

The Saudi attack highlights the diminishing role played by the United States in the region.  It represents a fundamental shift in the strategic situation as the Saudis and other Gulf states move into the vacuum created by the disappearance of American power.

It bears mentioning that half the world's oil supply skirts the coast of Yemen as tankers move through the Gulf of Aden.  Oil prices surged 4% on the news of the Saudi attack.