During World War I, diplomats from France, Britain, Tsarist Russia and Italy held secret meetings at which they discussed the territorial division of the Middle East in the event of an Allied victory and the collapse of the Ottoman Empire. The agreement reached in 1916 - officially the Asia Minor Agreement - was later termed the Sykes-Picot agreement, after the top British and French officials at the talks, Sir Mark Sykes and Francois Georges-Picot. The agreement became public after the overthrow of the Tsar, when Soviet leader Leon Trotsky published its details in late November 1917. Implementation of the agreement after the war ended was also hindered by the founding of the modern Turkish republic under Mustafa Kemal "Ataturk" and revolts against British and French authority in Iraq and Syria respectively. 2 - DIVIDED IRAQ Iraq is divided broadly into three major communities: Arabs who follow Sunni Islam (the majority in the wider Arab world and dominant under Saddam Hussein), Arabs who follow Shiite Islam (the majority in Iraq itself, dominant today) and Kurds, an ethnic group that includes Sunnis and Shiites. After no-fly zones were instituted over northern Iraq following the first Gulf War, Kurdish regions in Iraq became increasingly autonomous, a situation that was formalised with Saddam's overthrow in 2003. Massoud Barzani is the current president of the Kurdistan Regional Government. The dominant force in the Shiite community since 2009 has been an electoral coalition known as State of Law, led until recently by Iraqi prime minister Nouri al-Maliki, although Shiites also look for leadership to religious scholars, the most senior being Grand Ayatollah Ali al-Sistani. The Sunni community's leadership, including tribal chiefs such as Sheikh Ali Hatem al-Sulaiman al-Dulaimi, has struggled to assert itself in the new Iraq.

3 - AN INVISIBLE NATION: KURDISTAN Kurds are predominantly Sunni Muslim but have their own language and culture separate to that of their neighbours, the Arabs, Turks and Persians. There are major Kurdish populations in Iran, Turkey, Iraq and Syria, each experiencing varying degrees of hostility from those states, who perceive them as a separatist force striving for a nation of its own. In Iraq, the leading Kurdish parties are the KDP (led by the Barzani family) and the PUK (which includes the current Iraqi President, Fouad Massoum, and is led by his predecessor as Iraqi president, Jalal Talabani). The Turkish government is currently engaged in a peace process with the Kurdistan Workers' Party or PKK and its imprisoned leader Abdullah Ocalan. Turkey had tried to stamp out the PKK by force over decades, and the PKK is listed by many Western countries as a terrorist group. Most Kurds believe that the principles set out in the post-World War I Middle East settlement by US president Woodrow Wilson among others committed the international community to the creation of an independent homeland for Kurds, but that subsequent political developments resulted in the West reneging on that commitment. 4 - THE RISE OF ISLAMISM

The 1979 revolution in Iran put Shiite Islamism on the map, and today many Iraqi Shiites belong to Islamist groups supported by Iran. Combined with the Soviet invasion of Afghanistan that year, the rise of Iran's Islamic Republic - led by Ayatollah Ruhollah Khomeini - spurred a new groundswell of militant Sunni Islamism, marked most dramatically by the attempted seizure of the Grand Mosque in Mecca in November 1979, an attack led by a Saudi called Juhayman al-Otaibi. The brutal suppression of these Sunni Islamists by regimes across the Arab world led to their increasing radicalisation, culminating in the formation of the group known as al-Qaeda in Afghanistan in the late 1990s. Al-Qaeda and its offshoots reject the national borders of most Middle East states as manmade and colonialist, and ISIL - the militant group that currently holds swathes of eastern Syria and northern Iraq - is the most extreme expression of this view. 5 - THE MONEY TAP: SAUDI ARABIA

The series of events in 2011 known as the "Arab Spring" threw the long-standing political architecture of the Middle East as a whole into turmoil, with the fall of dictators in Egypt, Tunisia, Libya and Yemen as well as a major challenge to the Syrian dictatorship and the monarchy in Bahrain. The response of Saudi Arabia to these events has been to bankroll the restoration of military rule in Egypt under Abdel-Fattah al-Sisi, to fund rebels in Syria and send troops and tanks into Bahrain to prop up its ally, as well as cracking down on its own Shiite minority. However, the rise of extreme militant Sunni Islamists in Syria and Iraq - even though those extremists come largely from the same theological tradition as the Saudi regime itself - has forced Saudi authorities to crack down on funding and support for Syria's rebellion and to give $1 billion to the Lebanese military to shore up its authority, a move announced by Lebanese Sunni leader and former prime minister Saad al-Hariri. These measures come at a time when the second generation of Saudi leadership - the many sons of the nation's founder, Ibn Saud, who have succeeded one another - are dying out. King Abdullah, the current monarch, is 90 years old and in failing health, yet he has outlived two crown princes. 6 - THE 'HEAD OF THE SNAKE': IRAN The US-led coalition that invaded Iraq in 2003 with the proclaimed aim of liberating the country created a situation where the country's dominant demographic group - Shiite Arabs with strong cultural and political ties to Iran - became politically dominant as well. This guaranteed that Iran's influence in Iraq increased massively, and led US allies in the Arab world such as Jordan, Egypt and Saudi Arabia to warn of a destabilising "Shiite crescent" stretching from Iraq through Syria to the Shiite militant group Hezbollah, led by Hassan Nasrallah, in Lebanon.

In recent years, Iran has moved to prop up the regime of Bashar al-Assad in Syria and is now trying to prop up the Iraqi government in Baghdad. But the Islamic Republic, led by Ayatollah Ali Khamenei, still considers the US and Israel to be its main opponents in the region, with the main point of contention its nuclear program, which it insists is for peaceful power generation but which the US and its Middle East allies believe is already a weapons program. A 2008 US diplomatic cable released in 2010 by WikiLeaks quoted Saudi King Abdullah urging Washington to "cut off the head of the snake". At the same time, the Iranian theocracy is struggling with internal demands for political reform, which came to a head after the controversial 2009 presidential election and led to the Green Movement protests of 2009-10. Maher Mughrabi is Foreign Editor for The Age and The Sydney Morning Herald.