Previously we reported that in the latest "coup" for US foreign policy, the US had "lost" over $500 million in weapons in Yemen, until recently an Obama administration foreign policy "success story", following the abrupt evacuation of the US embassy there, all of which ended up in local rebel and al-Qaeda hands.

It didnt take long for the local Houthi rebels to put all these weapons to good use: as Reuters reports, Houthi forces in Yemen backed by allied army units seized a key air base on Wednesday and appeared poised to capture the southern port of Aden from defenders loyal to President Abd-Rabbu Mansour Hadi, local residents said.

As a reminder this is the second time the Yemeni president, so close to Obama, will be forced to uproot and get out of Dodge, after his prompt "evacuation" from the capital Sanaa a month ago:

The Houthis and their military allies later advanced to within 40km (25 miles) of the city, where Hadi has been holed up since fleeing the groups stronghold in the capital Sanaa last month.

Yemens slide toward civil war has made the country a crucial front in mostly Sunni Saudi Arabias rivalry with Iran, which Riyadh accuses of sowing sectarian strife through its support for the Houthis.

Sunni Arab monarchies around Yemen have condemned the Houthi takeover as a coup and have mooted a military intervention in favor of Hadi in recent days.

The situation in Yemen is "fluid" but not looking good for the status quo: in Aden, heavy traffic clogged Aden as parents brought schoolchildren home and public sector employees obeyed orders to leave work. Eyewitnesses said pro-Hadi militiamen and tribal gunmen were out in force throughout the city

This happens as the northern militia alongside army units loyal to Yemens powerful ex-president Ali Abdullah Saleh have driven back an array of tribal fighters, army units and southern separatist militiamen loyal to embattled president Hadi.

The Iranian-backed Houthi Shiite militants took control of Sanaa in September and seized the central city of Taiz at the weekend as they move closer to Aden.

Houthi leaders have said their advance is a revolution against Hadi and his corrupt government, and Iran has blessed their rise as part of an "Islamic awakening" in the region.

Yemeni officials denied reports that Hadi had fled Aden.

Next up: yet another regional civial war involving a regime that was until recently so very loyal to Obama: a war which many blame on the former administration:

While Hadi has vowed to check the Houthi push south and called for Arab military support, his reversals have multiplied since heavy fighting first broke out in south Yemen on Thursday and the Houthis began making rapid advances southward.

In Houta, storefronts were shuttered and residents reported hearing bursts of machine gun fire and the bodies of fighters from both sides lying in the streets. Eyewitnesses said Houthi fighters and allied soldiers largely bypassed the city center and traveled by dirt roads to the southern suburbs facing Aden.

While the battle is publicly being waged by the Shiite Muslim Houthi movement, many Adenis believe that the real instigator of the campaign is former president Ali Abdullah Saleh, a fierce critic of Hadi. It was Saleh who was the author of the citys previous humiliation in 1994, when as president he crushed a southern secessionist uprising in a short but brutal war.

A body of army loyalists close to Saleh on Wednesday warned against any foreign interference, saying in a statement on Salehs party website that Yemen would confront such a move "with all its strength."

Which is ironic because according to AP, whats left of the government is now actually calling for its neighbors to invade the country to restore peace and stability!

And as a follow up Reuters reports, the Saudi are indeed preparing for what appears to be the next MENA war, by moving heavy military equipment including artillery to areas near its border with Yemen, U.S. officials said on Tuesday, raising the risk that the Middle East’s top oil power will be drawn into the worsening Yemeni conflict.

The slide toward war in Yemen has made the country a crucial front in Saudi Arabias region-wide rivalry with Iran, which Riyadh accuses of sowing sectarian strife through its support for the Houthis.

Just as Ukraine is a proxy war between Russia and the US, Yemen will be a proxy war between Iran and Saudi Arabia:

The conflict risks spiraling into a proxy war with Shiite Iran backing the Houthis, whose leaders adhere to the Zaydi sect of Shiite Islam, and Saudi Arabia and the other regional Sunni Muslim monarchies backing Hadi.

The armor and artillery being moved by Saudi Arabia could be used for offensive or defensive purposes, two U.S. government sources said. Two other U.S. officials said the build-up appeared to be defensive.

One U.S. government source described the size of the Saudi buildup on Yemens border as "significant" and said the Saudis could be preparing air strikes to defend Hadi if the Houthis attack his refuge in the southern seaport of Aden.

Another U.S. official, speaking on condition of anonymity, said Washington had acquired intelligence about the Saudi build-up. But there was no immediate word on the precise location near the border or the exact size of the force deployed.

As a result, the Saudis would reather shoot first, ask questions later:

Saudi Arabia faces the risk of the turmoil spilling across its porous 1,800 km (1,100 mile)-long border with Yemen and into its Shiite Eastern Province where the kingdoms richest oil deposits lie.

“The Saudis are just really deeply concerned about what they see as an Iranian stronghold in a failed state along their border,” U.S. Ambassador to Yemen Matthew Tueller told Reuters on Monday at a conference hosted by the National U.S.-Arab Chamber of Commerce in Washington.

But a former senior U.S. official, speaking to Reuters on condition of anonymity, said the prospects for successful external intervention in Yemen appeared slim. He said Hadi’s prospects appeared to be worsening and that for now he was “pretty well pinned down.”

Slim or not, the countdown to another proxy war has begun. The biggest winner? These guys.