Saudi Arabia, in coordination with several other Arab states, has started airstrikes against Houthi controlled positions and bases to stem the tide of their military advance. Riyadh has warned that the operation is only in its initial phase.
We don't know yet the scope and duration of the plan of attack, or how long this could last and if the Houthis decide to resist the intervention.
The United States has given the green light to the Saudi military action and has reportedly provided logistical assistance and intelligence to the Saudi-led military intervention.
We don't know the real nature of the support or the extent of Washington's commitment for a long military campaign. Is this a case of leading from behind?
Weaken but not defeat
As we've seen in other Middle East interventions, airstrikes are sure to weaken but not defeat the likes of the Houthis. It remains to be seen whether the Saudis have the will or the capacity to attempt alone or in operational coordination with others, a land offensive. That would totally change the strategic calculus in the Gulf region.
Saudi officials claim that their decision to intervene has come in response to the request by the fleeing Yemeni president and after the Houthis broke all understandings and continued their aggression against Yemen's legitimate government.
It remains to be seen whether the military action will quicken a return to more serious negotiations over the future of power sharing in Yemen, although it seems less realistic in the near future.
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Since taking over Sanaa last September, the Houthis have been making major advances through Yemen, reaching the southern city of Aden.
But it wasn't clear how the Houthis could have maintained control over all regions of Yemen and the population or whether the country would have descended into a full fledged civil war with the likes of al-Qaeda and ISIL playing a major role as in Iraq and Syria.
The Houthis tried to stay away from any border contact or confrontation with the Saudis to avoid a repeat of the 2009 Saudi airstrikes against their positions in the north. However the sudden surge and encroachment of the Houthis in the south prompted the Saudis to act.
Special army units loyal to the deposed President Ali Abdullah Saleh have supported the well-organised Houthis and helped the collapse of the military support for President Abed-Rabbu Mansour Hadi.
But it's rather surprising and largely vague as to why the former president has been allowed continued access to the military despite his removal form power in a deal brokered by Saudi Arabia and the GCC.
The Houthis tried to stay away from any border contact or confrontation with the Saudis to avoid a repeat of the 2009 Saudi airstrikes against their positions in the north. However the sudden surge and encroachment of the Houthis in the south prompted the Saudis to act. It's not clear as to why Riyadh has waited so long to put pressure.
There's been growing discomfort in Yemen by the aggressive campaign by the Houthi minority to take control of the country. But it's not clear these Yemenis will take kindly to long term "foreign" military presence in their country.
It's certain that this will prove to be a long and protracted conflict as the country descends into a full-scale civil war. Despite the countless reports about the first day's casualties, losses and retreats and advances, it's terribly difficult to come up with any reliable balance sheet at this early stage of the conflict or how this is bound to evolve or devolve in the coming days. The fog of war will continue to blur the reality on the ground for some time to come.
Iran has condemned the Saudi led military "aggression", while Riyadh has accused Iran of standing behind and supporting the Houthi takeover as part of its strategic attempts at regional control. It's not clear how Iran will react to the Saudi move.
Iran has overreached in a number of ways and in a few countries in the region, including Yemen. The Iranian Saudi proxy type conflicts are evident in various parts of the region, starting with Lebanon, Iraq, Bahrain, Syria and Yemen.
It's not clear whether Iran could sustain such an expansion of influence or act directly beyond Iraq. Or whether Saudi and Iran continue to exercise more influence in their immediate surroundings.
And since Iran has nurtured and groomed clients and allies in Iraq and Syria, the Saudis seem finally determined to stem the rise of Iranian influence on their southern borders and deny Iran access to the Red Sea and to the port of Aden.
Saudi Arabia is sure to ask for - and receive - Arab support during the Arab League summit that will be held in Egypt this weekend.
But it's not clear how far the Arabs are ready to go beyond symbolic gestures and provide direct support for the forces involved in the fight in Yemen. There's no precedent of coordinated Arab military campaigns.
What we also know is that Yemen is no Bahrain. It's a far bigger, heavily armed, more diverse and complicated nation. If the Saudis were able to stabilise in Bahrain in 2011 under the pretext of fighting Iranian influence, Yemen will prove to be a far more difficult task.
Now that Iran intervened in Iraq, Egypt and UAE carried out airstrikes in Libya, and Saudi entered Yemen, will Turkey finally intervene in Syria?
As the region moves to a whole new era, so many new questions, so few answers.
Marwan Bishara is the senior political analyst at Al Jazeera.
The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial policy.
Source: Al Jazeera