Saudi Arabia, the leading country in the Sunni world, shares with Yemen a long and largely porous border which runs to some 1,800 kilometres.

That alone encourages the kingdom to take an interest in what is happening in its troublesome neighbour to the south and it is hardly surprising that it decided to act when the Shia Houthis swept into power in Sanaa at the end of last year. Just as bad the new realignment seemed to give Iran the opportunity to interfere by influencing events in the Arabian peninsula. Saudi Arabia could not allow a situation like to develop just as it did as recently as 2011when it sent armed forces into Bahrain following a Shia- supported rebellion.

This time round Saudi has gone several steps further by forming a nine-nation coalition of mainly Arab states to help it restore order in Yemen. Officially the move has been made in direct response to a formal request from the deposed President Abd-Rabbu Mansour Hadi for military assistance from the Gulf Cooperation Council (GCC) but this is only diplomatic cover. Behind the scenes the Saudis are deeply concerned that they are facing a major strategic threat mounted by an increasingly aggressive Iran to establish its strategic hegemony in the Middle East and they need to nip it in the bud.

That accounts for the strength and depth of the Saudi coalition currently operating in Yemen this weekend under the title "Operation Decisive Storm". On paper it is a potent force with contributions from the following countries - Morocco, Egypt, Jordan, Sudan, Pakistan, Qatar, Kuwait, Bahrain, and United Arab Emirates - but to date its actions have been limited to air strikes and the deployment of naval forces in the Gulf and the Red Sea. Although these are useful assets experience has shown that in operations of this kind such as the recent Nato deployment against the Islamic State eventually serious thought has to be given to the insertion of ground troops.

The question is under discussion this weekend but any decision will not be taken lightly. The Middle East has recent and bitter experience of the kind of insurgency that can be provoked by the insertion of ground forces and one of the coalition partners, Egypt will remember only too well the bloody nose it received when it interfered in Yemen in the 1960s. Its leader at the time was President Gamal Nasser and he later claimed that Yemen was his Vietnam. Even so, Egypt's current minister of foreign affairs, Sameh Shoukri, surprised the Arab world when he announced at the end of last week that his country was willing "to send ground forces if necessary" to back the anti-Houthi fight. Others may follow but most GCC countries have so far refused to make any commitment.

According to the Saudi-owned al-Arabiya News, Saudi Arabia has dedicated 100 fighter jets, 150,000 soldiers and navy units to the current operation in Yemen and has vowed to continue until the Houthis have been defeated and Hadi's government is returned to power.