Last week Saudi Arabia entered the civil war in Yemen after Iran-backed Shiite Houthi rebels conquered the outskirts of the southern city of Aden. This was the first time the monarchy directly intervened in the bloody Sunni-Shia struggle that has devastated Syria, Iraq and Yemen.

Until now Saudi Arabia limited its involvement in that battle, to financial and military support for Sunni militias and armies.

Last year for example Saudi Arabia pledged $3 billion to the Lebanese army to strengthen its capabilities. The move came after Hezbollah won the battle in Qusair in Syria and threatened to change the power balance in the region. There were also reports that Islamic State received aid from Saudi Arabia at the start of its conquest of parts of Syria and Iraq.

Fighter planes of Saudi Arabia’s Air Force aided by jets from the other Gulf states, Jordan, Egypt, Sudan and Marocco have targeted numerous Houthi bases, rocket launchers and weapon depots since the begin of the air campaign four days ago. The air assault dubbed “Operation Determination Storm” has succeeded to drive the Houthi’s out of contested air bases and has destroyed all military aircraft in Yemen. The state-run Saudi Press Agency claimed that most launching pads for Yemen’s Scud missiles were now destroyed.

Saudi Arabia has amassed 150,000 soldiers along the border with Yemen, but no ground operation is expected. Ground forces operations are limited to securing the border and shelling of Houthi militias located opposite to the Saudi southern border.

The Saudi-led coalition received full support of the Arab League. During a summit of the League in Egypt on Saturday, the idea of the creation of a regional Arab military force  was discussed. President al-Sisi of Egypt was one of the Arab leaders who came out in support of the creation of such a force which is meant to counter the rise of the Iranian axis in the Middle East.

The decision by Saudi Arabia and other Sunni Arab countries to intervene directly in Yemen is connected to the failure of the U.S. operations in the country and certain developments involving Iran.

The U.S., in coordination with the now ousted Hadi regime, had been waging a drone-led anti-al-Qaeda offensive in Yemen. But two weeks ago the U.S. Army evacuated a base housing 100 troops. The move was a response to the offensive of the Houthi force and came after the closure of the U.S. Embassy in Yemen at the end of February.

The Saudi Arabia-led Gulf Council Cooperation (GCC) and other Arab Sunni states such as Egypt realize they cannot longer rely on the United States to protect them from Iran and Islamists groups. They saw the failure of the Obama administration to put an end to the chaos in Syria, Iraq, Libya and Yemen. They witnessed the engagement of the Obama administration with their enemy Iran and the negotiations about Iran’s nuclear program which will likely result in a deal that is unacceptable to the Arabs. They were in shock when the U.S. allowed Iran and the Islamic State to take over Iraq after the withdrawal of U.S. forces. They were flabbergasted when Obama refused to help Egypt in her fight against Islamic State affiliate Ansar Bayt al-Maqdis in Sinai while at the same time U.S. airplanes bombarded IS positions in Syria and Iraq.

They understood that the Obama administration does not have a coherent strategy in the Middle East as the U.S. in one country supports an Iran-backed Shia coalition fighting a Sunni force (ISIS in Iraq) and in another Arab country sides with a Sunni coalition fighting an Iran-backed Shiite militia ( Houthi’s in Yemen). The U.S. provides logistical and intelligence support to the Saudi-led coalition.

So when the Houthis took over Yemen and threatened to seize the strategic Bab al-Mandeb Straits, Iran finally crossed Saudi Arabia’s red line.  By seizing Bab-el-Mandeb Iran would have been able to control two strategic waterways that are vital for the supply of Arab oil to the world.

But that was not the only reason the Gulf States intervened in Yemen. As I reported earlier, Iran’s actions in Yemen could be a prelude to an assault on Saudi Arabia and that is the reason the country has amassed 150.000 soldiers along the border.

Here’s what I wrote at the time:

“Shortly after the turmoil in the Arab countries started, the Iranian regime produced a documentary in which it explained the chaotic events from the perspective of the Hadith. The intention of the movie was to show that the crisis in the Middle East foretells the imminent arrival of the Shiite messiah Mahdi and the unification of the world under Islam. This process was to be led by the Islamic Republic of Iran.

Yemen was explicitly mentioned in the documentary as a country that would witness “a holy revolution” and would then serve as a beachhead in an ensuing assault on Saudi Arabia’s holy Muslim places Mecca and Medina. Since the beginning of the Shiite insurgency against the Sunni-dominated central government in Yemen in 2004, fighting has occasionally spread to the Saudi province of Jizan.”

The question is now what will Iran do.

Until now Iran has only issued condemnations of Saudi Arabia’s ‘aggression” in Yemen but the official Iranian news agency Fars News indicated that Iran might have a red line too. The agency published an interview with Mohammed al-Bakhiti, who is a senior member of the Houthi political council.

He issued a clear threat to Saudi Arabia about a possible ground operation:

“Any ground attack on Yemen will receive a rigidly harsh response. We have not responded to the Saudi aggressions in the past five days because we wanted to allow the Arab countries to reconsider their action and stop their attacks,” he said, and added “but from now on everything will be different”.

Al-Bakhiti described the Saudi-led alliance against Yemen as a moral crisis, and said, “Whatever the Arab conference decided about Yemen will end in serious crisis.”

As things stand now, both Saudi Arabia and Iran are not interested in a confrontation in Yemen. Such a confrontation will almost certainly spin out of control and spark a regional or even global war because non-Arab countries such as Pakistan and Sudan have already pledged alliance with the Saudi-led coalition.

As analyst Jennifer Dyer pointed out on Sunday, Iran’s main interest is to hold the territories the Houthi’s conquered. Iran’s al-Quds Force is already overstretched and running multiple operations in Syria and Iraq. The Iranians have showed that they have a lot of patience and are advancing their goals in a very calculated manner. The model for Yemen will most likely be a copy of Lebanon, Iraq and Syria where Iran, using proxies, slowly advanced her goals.

Whichever way this war works out it won’t go smoothly. Yemen will probably face the type of prolonged war that the country faced in the 1960s when Yemen was the arena for a proxy war between rival Arab powers.

For now the only party that suffered a decisive defeat in this war is the United States. The ouster of the last remnants of U.S. troops from Yemen has seriously compromised the ability to wage war against Al Qaeda in the Arab peninsula.

President Obama has announced the defeat of Al-Qaeda on numerous occasions but as we can see in Iraq (ISIS), Syria (ISIS and al-Nusra), Nigeria (Boko Haram), Libya (Ansar al-Sharia and ISIS) and Yemen (AQAP) the organization didn’t die with Osama Bin Laden. To the contrary, Al Qaeda is on the rise and will certainly be emboldened by the U.S. retreat from Yemen.

This article was first published at Western Journalism in the USA