If we take as a starting point the notion that countries and regions are defined by their geography, then neighbouring nations exist in a Venn Diagram of potent conflicting interests. The equilibrium of the Middle East Venn Diagram, always shaky, was comprehensively disrupted by the events of September 11, 2001. Two decades later, the Covid-19 crisis of 2020 has done nothing to ease any of the problems that have beset the region with the disruption in its balance of power. In fact, the fallout is accelerating the pressures from within and outside.<br/> Due to America's increased energy self-sufficiency, along with its own political issues, the overarching US influence on the area has narrowed to a few fault-line issues. This development has come as Chinese attention has grown. Russia, meanwhile, has secured its position in Syria and, with it, an increased presence in the eastern Mediterranean. The Iranian position, via its proxies and supporters, continues to strengthen, despite its domestic political fragility, compounded by demographic and economic factors. Where a people live – whether on the coast, in the mountains, on fertile river plains or in tropical, desert, temperate or icy climes – has long determined what they do and can do, or what can be done to them. Accumulated historical experiences feed into a people's sense of themselves, providing powerful feelings of inspiration, aspiration or grievance. Some regions of the world, long before the concepts of country, nation or state took hold, were a natural focus for ambition, competition and conquest, and their geography made them the natural conduit for marching armies and migrating peoples.<br/> One of these regions is Mesopotamia, the "land between the rivers" of the Tigris and Euphrates, and a birthplace of civilisations, empires and religions. Attractive to successive waves of nomadic predators, who in turn became settled imperial powers themselves, the area is bounded in the north by the Anatolian Plateau of modern Turkey, in the east by the Zagros Mountains and central plateau of Iran, in the south by the deserts of the Arabian Peninsula, and to the west by the Egyptian Nile and its Delta. This is the "cockpit" of the Middle East, and Egyptians, Arabs, Turks and Iranians have successively and concurrently looked to this rich region not simply for its legendary wealth, but for the "strategic depth" it offers.<br/> The territory between the Zagros Mountains and the Mediterranean has been dominated in its time by the Pharaohs of Egypt, the Achaemenid and Sassanian Empires of Persia, the Umayyad and Abbasid caliphates of the Arabs, the Egyptian Mamluks, the Ottoman Turks and more recently the imperial British and French.<br/> From the middle of the 7th century until the early 20th century, the region had a strong degree of linguistic, cultural and religious commonality through a largely Muslim, Arabic-speaking identity, encapsulated in the reality of the caliphate and the Islamic concept of the ummah. These characteristics were leavened by the Sunni-Shia confessional split and the presence of important and significant ethnic and religious minorities – not least Christians, Jews, Kurds and Druze.<br/> Any broader sense of unity that may have transcended this diversity was eroded by the Western depredations of the 19th century. It was shattered altogether by the collapse of the Ottoman Empire at the end of the First World War, as well as the subsequent abolition of both the sultanate and the caliphate by the founder of the Turkish republic, Mustafa Kemal Ataturk. The idea of a caliphate was ill-suited to the national aspirations of the 20th century. A failed effort by Abu Bakr Al Baghdadi, the leader of ISIS, to revive a false version of a caliphate via proclamation from Mosul’s Grand Mosque reflected the aspirations of those he claimed to represent poorly, too. In the aftermath of the First World War, the debilitated Turks, Iranians and Arabs fell back on their historical ethnic heartlands. The area between them was now occupied by the new, diverse, League of Nations-"mandated" entities of Lebanon, Syria, Palestine, Trans-Jordan and Iraq.<br/> This volatile arrangement, resented both by the former regional powers, and the inhabitants of these former imperial administrative districts, was broadly sustained until the early 21st century. It rested on a combination of a regional balance of power, supplemented by the global confrontation between America and the Soviet Union, and the robust approach to internal dissent by the rulers of Iraq and Syria.<br/> However, the uneasy nexus eventually gave way under pressure from competing ethnic and religious power centres, each with their own, powerful sense of historical entitlement.<br/> Iran shared a strong historical sensibility stemming from its imperial past, its cultural championship of Shi'ism from the 16th century and, more recently, by its revolution in 1979. The Turks, having renounced imperial pretensions under Ataturk, never really shrugged of a sense of imperial entitlement in the region, as has been increasingly demonstrated by the actions of President Recep Tayyip Erdogan.<br/> In this context, the combination of 9/11 plus the US decision to invade and occupy Iraq in 2003 was a pivotal and ill-fated moment. It helped to catalyse the spread of extremist ideology under Al Qaeda and then its equally murderous successor, ISIS.<br/> The process of empowering Iraq's Shia majority, which had been violently repressed by Saddam Hussein, not only sparked a violent Sunni backlash, but was also vulnerable to Iran extending its own influence throughout the country. These trends were all further accelerated by the events of the 'Arab uprisings' in 2011, and the descent of Syria into civil war.<br/> Thus a combination of fear, ambition and revanchism has led to all of the major regional powers taking an active role in contributing to the volatility and violence that has wracked Mesopotamia and the Levant in the past two decades. The US disengagement from Iraq, then Syria, following American growing disillusionment with its actions in the region, has further emboldened Tehran, which has been able to strengthen its hold on Baghdad, as well as Damascus and Beirut. It has been assisted by Russia, which decisively intervened in Syria to shore up the regime of Bashar Al Assad, in the wake of US reluctance to "punish" the regime for breaches of a chemical weapons ban. In response, there has been a realignment of many Arab states as they seek to confront the threat posed by Iran and its proxies, but also that of the extremism propagated by the Muslim Brotherhood. Turkey's government, led by Mr Erdogan, persists in its pretensions to former Ottoman greatness. It has sought to exploit the turmoil to offer protection to Turkic communities in neighbouring states while prosecuting a war against the Kurds in Turkey itself , Iraq and Syria. In addition, it has utilised extremist Syrian fighters in its proxy conflicts in Libya and Azerbaijan while offering support to Qatar in the latter's dispute with fellow Gulf states. Meanwhile Iran's nuclear ambitions remain shrouded in secrecy and obfuscation, while its ballistic missile programme continues apace – as does its support of terrorist groups.<br/> In the absence of any dominant or compelling organising principle for the area between the Zagros Mountains and the Mediterranean, the circles of the Middle East Venn Diagram, representing the competing interests of Arabs, Turks and Iranians, are overlapping and intractable. The long-term toll is the damage caused to the security, stability and prosperity of the region and its people. <em>Sir Simon Mayall is a retired British Army officer, Middle East adviser at the UK Ministry of Defence and author of the newly published personal history Soldier in the Sand.</em>