WHO are the Houthis and what are they trying to achieve?

The simple answer is that they are the followers of Hussein Badr al-Din al-Houthi who was killed while leading his people in the Saada province of Yemen in a first uprising in 2004. Their aim was to win greater autonomy and to protect their revivalist Zaidi religious and cultural traditions which have existed in the northern part of the country for the past thousand years.

They are also known as Ansar Allah (Army of God) and, as Shia Muslims, are opposed to the Sunni forces loyal to the former President Abdrabbuh Mansour Hadi whom they deposed in February, thereby plunging Yemen into civil war and sending him into exile in Saudi Arabia. Paradoxically, the Houthis are now acting in partnership with forces loyal to a former president Ali Abdullah Saleh whom they had originally helped to depose and was succeeded by his deputy Hadi.

A more complicated response is that although the Houthis have been demonised by Hadi and his supporters in Saudi Arabia, they represent one-third of the Yemeni population and their uprising has unsettled a strategically important country that sits on the Bab al-Mandab strait linking the Red Sea with the Gulf of Aden. It is through this narrow passage that the bulk of the world's oil shipments have to pass. A complicating factor is the presence in Yemen of Al Qaeda in the Arabian Peninsula (AQAP), which opposes both the Houthis and the former president and this has led to further violence and destabilisation.

As if this were not sufficient to alarm the outside world in a region which is already volatile, the fighting in Yemen has taken on the aspect of a proxy war. The Houthis receive most of their military and financial support from their Shia co-religionists in Iran while the deposed President Hadi made an appeal to the Sunni world to come to his assistance and help restore him to power. Led by Saudi Arabia, a coalition was formed in March this year consisting of Morocco, Egypt, Jordan, Sudan, Pakistan, Qatar, Kuwait, Bahrain, and United Arab Emirates but it has done little other than mount air strikes against Houthi positions which have killed 2800 civilians. The coalition has also imposed a naval blockade which has created a humanitarian aid crisis affecting 21 million people while doing nothing to stop the fighting.

While the Saudi air strikes have offered close air support to the government forces supporting the deposed president and in so doing have destroyed heavy weaponry, they have also shown up the limitations and weaknesses of air power. Many of the casualties have been civilians - a result of poor targeting and faulty intelligence - and this has led to a weakening of existing support for Hadi and his government. All this has alarmed senior US military commanders - Saudi's main western ally - who fear that it could play into the hands of AQAP, regarded in Washington as the most lethal of Al-Qaeda's remaining affiliates or franchises.

In an attempt to put the Saudi operations in a good light, Brigadier General Ahmed Asiri of the Saudi army urged critics to remember that similar operations in Afghanistan took Nato a decade to achieve anything and he also claimed that many of the civilians deaths were not the coalition's responsibility.

"The Houthis are controlling the ground," he said in a press conference in Riyadh last week, "and if you are fighting among civilians, having your checkpoints everywhere, you will come up with this kind of casualties." As happens so frequently in this kind of internecine conflict, the blame game is an important part of the propaganda war and as things stand this weekend the Saudis are not winning it.