Across many parts of the Muslim world, 2013 is set to be a turbulent and bloody year as secularists battle with religious hardliners, tensions sharpen between the two rival camps of Islam and traditional power bases and hybrid political systems are challenged by a social-media-savvy young generation.
In Tunisia and Egypt, where dictators were overthrown in the 2011 Arab Spring, Islamists have won at the ballot box but struggle with accusations of economic incompetence and meddling with secular laws and human rights.
Libya is in turmoil, rocked by militia groups and attacks by jihadists, including an assault that killed the United States ambassador. In Syria, meanwhile, a Lebanon-style civil war beckons.
"2013 will definitely be a make-or-break year for Egypt, Tunisia, Libya and Sudan, which are sliding into Islamism; for Syria, Nigeria, Morocco, Jordan and the Sahel countries, which are borderline; and for Pakistan and Saudi Arabia, which are already Islamised," says Alain Chouet, a Middle East specialist and a former deputy of France's external intelligence agency.
He points at Western countries which failed to spot the dangerous vacuum left by the downfall of autocrats and at the risks posed by the petrodollar monarchies of Saudi Arabia and Qatar.
The Gulf countries' financial - and probably armed - support for Sunni extremists is driving radicalisation in Arab Spring countries and stoking a feud with Iranian-backed Shia Muslims.
The perils of sectarianism are most visible in Syria, which is predominantly Sunni, has a large Shia minority and is run by Alawites, a once-persecuted Shia offshoot that accounts for about a seventh of the population. Alawites fear being massacred because of their association with Bashar al-Assad's rule, and this is deepening the conflict.
"Suggesting to them and other non-Arab or non-Sunni minorities in Syria that they should accept changes that bring Salafist Islamists to power is the same as if you asked African-Americans to return to the situation that prevailed before the American Civil War," Chouet contends.
Sunnis account for 87-90 per cent of the world's 1.6 billion Muslims, and Shias for about 10-13 per cent, according to an analysis by the American Pew Research Centre.
The bust-up dates to the succession of the Prophet Muhammed as leader of the world's Muslims in the early seventh century. The initial row dragged on bloodily for decades, stoking martyrdom among Shias. In recent years, violence and unrest have flared in Pakistan, Iraq and Bahrain. Many Shias do not recognise Sunni elected officials and teachers, and many Sunnis do not count Shias as fellow believers.
Of seven Middle Eastern-North African countries where Pew carried out its survey on Muslim beliefs, only Iraq and Lebanon had large majorities of Sunnis who accepted Shias as being of the same faith.
"The Sunni-Shia divide has been in the Muslim world for centuries and in many countries they have learned to live with each other," says Basil Mustafa of the Oxford Centre for Islamic Studies. "The clash is of a more recent nature. Part of it is due to a strand of religious radicalism that has surfaced on both sides, in all communities."
Several ingredients add unpredictability to the explosive mix facing the Muslim world. They include a succession crisis in Saudi Arabia, where younger citizens are clamouring for the grip of the Wahhabi clerical establishment to be eased and for constitutional monarchy.
The present king, Abdullah bin Abdulaziz, an ailing 89-year-old, carried out cautious reforms only to shelve them in the face of Shia revolts in the eastern part of the kingdom, which were blamed on Iran.
Two crown princes, Sultan, 86, and brother Nayef, 76, have died within just eight months. Unlike other monarchies, succession within the sprawling al-Saud clan is not transmitted from father to the oldest son. Instead, succession is chosen by the king and senior family members in the interests of keeping stability among the family's many branches. Polygamy ensures that there are lots of crown princes to choose from.
The current designated successor is Defence Minister Prince Salman bin Abdul Aziz, 76, whose choice stifles hopes of a "generational leap" towards younger rulers.
Another wild card is Israel, whose settlement expansion in East Jerusalem and the West Bank is hurting hopes of a two-state solution with the Palestinians.
Israeli Prime Minister Benjamin Netanyahu is basing his campaign for the general elections on January 22 on his threat to halt Iran's perceived march towards nuclear weapons. The poll will be held six days after the United Nations' International Atomic Energy Agency meets Iran over opening its sites to outside inspection.
"For several years now, we've been talking about the push-comes-to-shove moment arriving in Iran, and that moment may come in 2013 since the Iranians seem to be creeping closer and closer to what are presumed to be the red lines on its nuclear weapons programme," predicts James Lindsay of the Washington-based Council on Foreign Relations.
"One possibility is this leads to negotiations and we get a compromise agreement that stops Iran short of possessing a nuclear weapon, or the capacity to build one quickly."