The Saudi execution of dissident Shia cleric Nimr al-Nimr has already deepened the regional rift between Sunni Saudi Arabia and Shia Iran.
Iran's supreme guide, Ayatollah Ali Khamenei, said the kingdom will face "divine revenge" for killing a scholar who did not encourage Shias to conduct armed struggle against their Sunni rulers or plot against the country's government.
His use of the phrase "divine revenge" suggests Iran will take no direct action against Saudi Arabia. However, Iran could exact indirect retribution by providing serious military support to Shia Houthi tribesmen battling the Saudi-led Sunni coalition for control of Yemen.
Saudi Arabia intervened in the conflict between the Houthis and the Yemeni government in March. The campaign has not gone well and has, in nine months, devastated Yemen and driven hundreds of thousands of Yemenis from their homes.
Iran is unlikely to deepen its already major involvement in the war in Syria, where Tehran supports the government against an array of armed groups, some of which have Saudi backing in the war to overthrow the regime.
Assad ally
Still, Iran can complicate current efforts aimed at imposing ceasefires on both pro- and anti-government factions. It could insist that president Bashar al-Assad remains in power during a proposed transitional period and even stand for re-election once a new constitution is adopted. Both scenarios are rejected by the Saudis and their Arab and western allies.
Following the deaths of hundreds of Muslim pilgrims in a crush during last year’s Hajj, Tehran could also argue that Saudi Arabia is not fit to manage the event and call for it to be handed over to a body established for this purpose.
This would deprive the Saudi ruler of the right to assume the title of the “Guardian of the Two Holy Mosques” of Mecca and Medina, a title the Saudis invented to lay claim to these sacred sites. Losing the Hajj would also deprive the Saudis of billions in revenue.
The Iraqi Shia fundamentalist-led government, a close ally of Tehran, has been placed in a difficult position at a time when Riyadh had just reopened its embassy in Baghdad, closed in 1990 after the Iraqi invasion of Kuwait. The Saudi aim was to normalise relations with Iraq, reducing the Shia-Sunni rift.
Martyred sheikh
Iraq’s senior Shia cleric, Grand Ayatollah Ali al-Sistani, has condemned the execution and referred to Sheikh Nimr as a “martyr”. Conferring on him the title of “martyr” confirms him as a “hero” of the Shia branch of Islam, which is considered an aberration rather than a legitimate wing of the faith by Saudi puritans.
Shias have a very long list of “martyrs”, including imams, beginning with Ali, the son- in-law of the Prophet Muhammad, and his grandsons, Hassan and Hussein. Their histories distinguish Shia from Sunni. Furthermore, Shias have not forgotten that Saudi Wahhabi warriors sacked the Shia holy city of Karbala in 1802, killing 5,000 inhabitants.
Shia outrage over the execution of Nimr could explode if the method of execution becomes public. He was sentenced to death by a Saudi court in October 2014 for seeking “foreign meddling” in Saudi affairs, “disobeying its rulers”, and taking up arms against the security forces.
He was, reportedly, sentenced to die by crucifixion, but it is not clear how the execution was carried out. Forty-six other men were killed by decapitation or shooting.