"We really need to think about Yemen more holistically. We have been focusing on a short-term, localized counterterrorism problem without doing anything to significantly help build the state and help build the society."- former U.S. Ambassador Barbara Bodine

The conflict in Yemen will not be over quickly.  Yemen has been fractured along several religious and political lines for decades, so no solution will be quick and easy in the beleaguered country (check out this previous post on Yemen for more details).  Just last week, the Houthi rebels took over much of Yemen's port city Aden (they have already taken most of the capital) and succeeded in driving former Yemeni President Abd Rabbuh Mansour Hadi from the country.  To further complicate matters, Saudi Arabia launched a series of airstrikes (known as Operation Decisive Storm) in Yemen with the help of a broad coalition of regional allies (Egypt, Jordan, UAE, and others, along with some intelligence support from the U.S.).  And finally, we have the Arab League approving the idea of a joint military force to combat regional threats (essentially anything that could be considered Iranian influence).  So what's the end game for Saudi and friends with the possibility of a ground intervention looming on the horizon? 

First, what is the Arab League anyway?  The League of Arab States is an international organization (like the U.N.) where the predominantly Arab nations of the world gather to share ideas on transnational issues and pass non-binding resolutions.  For now, they have only passed a resolution on a joint military force, which means they "support the idea" but are not yet actively joining forces as a single organization.  The Gulf Cooperation Council countries (Saudi Arabia, Kuwait, Oman, Qatar, Bahrain, and the UAE) had a similar idea in 1984, creating the joint military brigade known as the Peninsula Shield Force.  To date, this force has only been deployed three times, most recently in Bahrain to put down predominantly Shia protests there.  If activated, the Arab League force would probably fulfill a similar role.

However, the force of regional allies preparing a potential invasion in Yemen is far more established than the Arab League proposal.  This endeavor is being led for the most part by Saudi Arabia, and the Kingdom has a history of armed intervention in Yemen.  This isn't surprising given theover 1,000 mile long border the two countries share, and the security problems of this very desolate border.  In the 1960s, Saudi Arabia intervened in the North Yemen Civil War to support soldiers loyal to the monarchy (ultimately they lost).  More recently in 2009, the military launched a limited ground offensive into Yemen called Operation Scorched Earth.  Just like recent events, this operation was conducted in order to stop the advances of the Houthis in northern Yemen.  If history is any indication, Saudi Arabia isn't shy about taking drastic measures to curb the influence of competing factions in Yemen. 

So, will history repeat itself and see another foreign invasion of Yemen?  It looks likely given the justifications for Saudi airstrikes and the deployment of over 150,000 soldiers to the Yemeni border.  The Kingdom has stated several times that they will take any means necessary to prevent a Houthi regime in Yemen, and that they will "gauge the effectiveness" of airstrikes in bringing Houthis to the negotiating table.  In their words, airstrikes will not stop until they "withdraw and surrender their weapons." It is hard to image the Saudis actually believe bombings will bring an insurgent group to negotiate with a country known for its ruthless prosecution of suspected terrorists.  Instead the Houthis will probably be driven underground, thus forcing an invasion.  Speculation about a Saudi led invasion has been growing with Yemen's ousted President Hadi calling on Saudi Arabia to launch a direct ground invasion.

What will this mean for the region?  First, the Saudi forces would have to push all the way south to Aden in order to fully maintain control.  Though much of Yemen is sparsely populated outside the major cities, this still won't be an easy task.  Once they have control, this will almost certainly start a protracted insurgency led by the Houthis as they embed within the population for protection.  Then there is the al-Qaeda factor.  Though the Houthis and al-Qaeda in the Arabian Peninsula (AQAP) share no love, an action which weakens the rebels without also installing a strong power in its place will leave significant room for AQAP to grow (even with Saudi forces and U.S. intelligence actively targeting them).   Ultimately, Saudi and friends would likely be fighting Houthis, AQAP, and any local militias seeking to remove foreign troops from Yemen.  It will get very messy and has the potential to spread more discontent throughout the region.

Then there is the political side of things.  As mentioned before, Saudi Arabia would basically have to either take full control of the country (unlikely given the serious commitment of several years that would take) or prop up a government (likely President Hadi) to do the heavy lifting for them.  Finding a leader that will please all of the "right" factions and subdue all of the dissenters in Yemen is no easy feat even during peacetime. Regionally, Saudi Arabia is feeling more and more threatened.  Iran has ties to Hezbollah in Lebanon and to the Iraqi government.  So the Gulf Arab nations are increasingly feeling surrounded by seemingly hostile forces.  It would be overly-simplistic to characterize all of these groups as merely puppets of Iran just because of their shared Shia Islam religion.  Still, Iran will likely use the local problems which give rise to these groups as a means to further its own influence in the region.   

Finally, there is the ever-present American factor.  U.S. intelligence has been providing support to the airstrikes, highly suggesting that the Intelligence Community has known about this plan for some time.  The U.S. is probably also interested in using this as a convenient way to attack AQAP in Yemen (potentially as a replacement for its drone strikes which were suspended when American officials evacuated the country).  America is also looking to check the aforementioned Iranian influence in the region, but its cooperation with Iran in the fight against ISIS and the success of thenuclear program negotiations show that the U.S. is more concerned about long-term stability than a marginalized Iran. 

In all, it seems that the Saudi Arabia and its allies mean business in Yemen.  Too much is at stake for them to back out now, and little can actually be gained through continued airstrikes alone. If this potential Arab League military force becomes more than just a signed piece of paper, it puts the Sunni Arab states on a more direct path towards confronting Iran directly via forces such as the Houthis in Yemen.  Still, we are unlikely to see another war on the scale of the Iran-Iraq War.  Most powerful nations prefer to fight via proxy wars (think the Cold War but with Arab nations) rather than confront each other directly.  These wars are fought over decades, and often take years for their effects to be fully felt.  In Yemen, what started as a series of regional disputes will almost certainly become another long, messy conflict.

TL;DR: There are no good solutions in Yemen, but there are plenty of bad ones.