Why is Saudi Arabia bombing Yemen?

Sunni Saudis and their partners contend the air offensive in Yemen is meant to halt Shia Iran's drive to expand its regional influence by backing Yemen's rebel Houthi tribesmen in their battle against Saudi-supported president Abed Rabbo Mansour Hadi.

However, Iran’s connection with the Houthis is marginal at best and Saudi Arabia’s new king, Salman bin Abdel Aziz, has powerful domestic reasons for waging a war. He is seeking to unify subjects split between ultra-conservatives and reformers, solidify his hold on power with a military victory, and prepare the way for a favourite younger son, Mohamed to ascend to the top rungs of the succession ladder.

Born to Salman’s third wife, Mohamed was given the key defence portfolio ahead of senior and more qualified brothers. Claimed to be aged 30-35 but said to be, in fact, 26, Mohamed is seeking to make a reputation for himself by waging a successful campaign.

This is a risky venture. The Houthis enjoy the backing of well-armed units of the Yemeni army and air force loyal to former president Ali Abdullah Saleh and are determined to counter the Saudi offensive, so far confined to air strikes.

The Saudis have already lost the battle for hearts and minds in the north due to the destruction wrought by their bombs; many south Yemenis reject Hadi’s return and all Yemenis fear al-Qaeda in the Arabian Peninsula, Islamic State and southern secessionists will use the fighting to seize territory.

Salman's ambitions and rivalries within the ruling family also appear to be driving him to alter policies adopted by late king Abdullah. In a bid to restore unity in the six-member Gulf Co-operation Council, Salman has patched up relations with Qatar, strained over Doha's support for the Egyptian Muslim Brotherhood and radical Sunni insurgents fighting in Syria and Iraq.

Salman, 79 and a stroke survivor, fears he may not have a long reign and is seeking to promote Mohamed while he can. Salman's half-brother Muqrin bin Abdel Aziz (69) is crown prince and Mohamed bin Nayef (55), the son of a third half-brother, is next in line. His appointment was meant to ensure a peaceful transition from the remaining elderly sons of the kingdom's founder Abdel Aziz ibn Saud to a competent grandson.

Salman appears to believe that if Mohamed succeeds as a warrior in Yemen he could top succession ladder but if he fails he could very well be relegated to the bottom rung.