When the highest religious authority in Saudi Arabia tells soldiers to be ready to lay down their lives, it isn't a routine sermon. The Grand Mufti, Sheikh Saleh bin Fawzan Al-Fawzan, sent a message to troops on the kingdom's borders: defend the land and be prepared to die fighting Yemen's Houthis, until the group has been completely removed from power. The message was published by the Saudi state news agency.

The mufti rarely speaks out this sharply. His message cites verses from the Quran and sayings of the Prophet Muhammad on sacrifice and struggle "in the way of God". "Protecting this great nation and punishing anyone who tries to grab even a span of its territory are among the greatest duties and noblest acts of piety, for which lives and souls may be sacrificed," he said. He told front-line soldiers to obey their commanders and rulers, because in doing so they "defend the holy places of Muslims".

The context explains everything. For weeks the Houthis have been pummelling Saudi Arabia with drones and missiles, and Riyadh has hit back with air strikes. The kingdom said it intercepted six ballistic missiles fired towards the west of the country and the Red Sea port of Yanbu, while the rebels claim they targeted sites in Riyadh itself and Saudi Aramco oil facilities. Oil prices on world markets immediately jumped by about three percent.

The strait that has the world by the throat

The real reason for the panic in Riyadh is on the map. Two weeks ago, rebel forces swept across Yemen's entire west coast in a rapid offensive and reached the Bab el-Mandeb strait - one of the most important shipping lanes in the world - taking it from Saudi-backed forces. Yemen's official government openly warned at the UN that, by controlling the strait, the rebels "are holding the entire world economy hostage".

The timing couldn't be worse. The attacks threaten Saudi exports via the Red Sea at the very moment passage through the Strait of Hormuz is also under strain. The rebels have declared a naval blockade of Saudi Arabia, and a key oil pipeline has also been hit by drones. If both main exits for Gulf oil are under pressure, how long will the price rise stop at three percent?

On land, the Houthis are pushing on the Hayjat al-Abd mountain pass to cut the last remaining supply route to Taiz, Yemen's third-largest city. If they succeed, government forces face total collapse.

When sanctions don't work, the sermons come out

Military analysts warn that Yemen's rebel army has grown into what is probably the most dangerous force in Iran's network in the Middle East. While Lebanon's Hezbollah has been weakened by Israeli strikes, the Houthis have proved more radical and more technically capable - they recently even shot down a modern Saudi F-15 fighter jet with an upgraded missile. Unlike other groups in the region, this army cares about neither the destruction nor public services: the money goes almost exclusively to fighting, and its driving force is an ideology of martyrdom.

Riyadh has called an emergency meeting of chiefs of staff with Turkey and Pakistan for today, under their joint defence pact. But in Pakistan there's growing concern that the country could be dragged into a long and bloody war in the Middle East. Alliances look solid on paper - until someone has to send troops.

International interventions and sanctions so far have produced nothing, so the Saudi leadership is now reaching for rare religious proclamations. The Balkans know all too well how it sounds when a state starts talking to its soldiers about sacrifice instead of victory. Does that mean the other options have already run out?