One of the less noticed resolutions of the Arab League summit on Sunday in Sharm el-Sheikh was the condemnation of Israel and Iran for "occupying Arab land". This meant the West Bank and, in Iran's case, some small islands in the Persian Gulf.

This standard nod to the old Arab nationalism, a brief throwback to the days before the Islamic Revolution in 1979, when Israel and Iran were strategic allies against the hostile Arab world, highlighted just how much has changed in recent years.

The main issue on the summit's agenda apparently did not involve Iran or Israel. The Arab leaders were there to pledge support for the Saudi-led offensive against the Houthi rebels in Yemen, and to approve the formation of a joint Arab force made up of 40,000 special-force troops, armoured units, warships and jets.

In both cases, the direct targets may be militant groups trying to overthrow governments, but the underlying motive is to minimise Iranian influence in the region. This is the Saudis' second deployment designed to ward off Iran: three years ago, they sent forces to back up the Bahraini government, which was facing an uprising by the Shiite majority.

The Yemen intervention, which began in the early hours of Sunday morning, is much larger, involving waves of air-strikes and a potential invasion of 150,000 ground troops.

It is being backed up by 10 other Arab states - most significantly Egypt - and it is coming at a pivotal moment for the region.

The nuclear deal between Iran and the international powers regulates the level of uranium enrichment and other technical factors necessary for the manufacture of an atom bomb. But for the main parties involved, particularly the United States and Iran, it represents an attempt by the Obama administration to transform their old enemy into an ally, a bulwark against radical groups such as Islamic State. Whether or not Obama's grand plan works, he has already succeeded in creating a different alliance - the anti-Iran axis whose main nodes are Jerusalem, Cairo and Riyadh. Benjamin Netanyahu and Egyptian President Abdel Fattah al-Sisi are relatively open about their close co-ordination. The Israel-Saudi ties are more under wraps, but their significance for the region's future is deep.

Yemen is just a warning shot that the Saudis mean business. The next stop is likely to be in Syria, where they plan to step up their support for Sunni rebels fighting the Iranian-backed regime and its vanguard, Hizbollah.

Syria is on Israel's border and the loss of Bashar Assad will be a strategic blow to Tehran of a much greater magnitude than a setback in Yemen.

Greater Saudi and Egyptian involvement in Syria, with Israel's tacit backing, could drag the entire region into the bloody civil war there, at a time when the Americans have made it clear to their old allies that they cannot rely on their support against Iran.