War is an ugly thing is clearly an understatement.

Then there is Aleppo, Syria.

WashingtonPost: In 1165, Benjamin of Tudela, a medieval Spanish Jewish traveler, approached the city of Mosul on the banks of the Tigris. A visitor, even a thousand years ago, could marvel at its antiquity. “This city, situated on the confines of Persia, is of great extent and very ancient,” he wrote in the chronicle of his journey. He gestured to the adjacent ruins of Nineveh, which had been sacked 15 centuries before his arrival.

Mosul, perched in Mesopotamia’s fertile river basin, was a walled trade city at the heart of the proverbial cradle of civilizations, linked to caravan routes threading east and other venerable urban centers like Aleppo to the west. It’s a city that has endured centuries of war and conflict, devastation and renewal. And even a millennium ago, though they couldn’t fathom its later uses, people were aware of Mosul’s great natural resource: Oil.

“To the right of the road to Mosul,” noted another 12th century Arab traveler, “is a depression in the earth, black as if it lay under a cloud. It is there that God causes the sources of pitch, great and small, to spurt forth.”

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Mosul in the Middle Ages

In the wake of the First Crusade, which led to a string of Christian Crusader states taking root along the eastern coast of the Mediterranean, Mosul became one of the main staging grounds for the Muslim riposte. At the time, the city was ruled by Seljuks, a Turkic tribe that had settled across swathes of the Middle East.

In 1104, an army led by the Seljuk “atabeg,” or governor, of Mosul marched west and routed a Crusader force on a plain close to what’s now the modern-day Syrian city of Raqqa, the de facto capital of the Islamic State. “For the Muslims, it was an unequaled triumph,” wrote one Arab chronicler. “The morale of the Muslims rose, their ardor in defense of their religion was enhanced.” In 1127, Imad ad-din Zengi became Mosul’s atabeg and went on to forge a regional empire that united Aleppo with Mosul and successfully took the Crusader fortress at Edessa.

Zengi’s dynasty, installed in Mosul, went on to rival both the Christian knights in the Levant and the Caliph in Baghdad. Even when the famed Kurdish general Salah ad-Din, the greatest Muslim hero in the history of the Crusades, took over a vast swathe of the Middle East toward the end of the 12th century, the Zengids of Mosul held out. Their resistance was broken in the following century — not by Crusaders or rival Muslim armies, but the conquering hordes of the Mongols.

Despite all the conflict, the city and its environs would preserve its diverse character and remain home to Muslims, Jews, Christians and other sects, as well as a busy commercial entrepot for all sorts of goods. Though produced much farther east in Bengal, the ultra-soft and light fabric known as “muslin” derives its name from Mosul, because that was the point from which this textile entered the European imagination.

An Ottoman province

By the mid-16th century, Mosul fell under Ottoman control following the successful campaigns of Turkish armies against those of Persia’s Safavid dynasty. Most of what we know as the Arabic-speaking Middle East now ruled by the Ottomans. The Ottoman-Persian rivalry, which included a dimension of Sunni-Shia strife, shaped the region’s geopolitics for centuries. The lands that now constitute Iraq, particularly its rugged north, would be the site of myriad border wars, skirmishes and sieges.

In the early 19th century, Mosul became the capital of an Ottoman vilayet, or province, that stretched over what’s now northern Iraq. After the empire’s collapse, British colonial rulers would stitch together the vilayets of Mosul, Baghdad and Basra — a sea port to the south whose environs were home to a mostly Shiite population — into the new nation of Iraq.

A legacy of Sykes-Picot

A British army marched into Mosul in 1918 toward the end of World War I, forever ending Turkish rule in Iraq. The map above, though, depicts a post-war settlement that never came about. The infamous Sykes-Picot agreement — a secret deal hatched in 1916 by the British and French diplomats whose name it still carries — carved up the lands of the Ottoman Middle East between rival spheres of British and French influence. In the initial scheme, Mosul would fall under a French protectorate; the city was seen as more closely linked to Aleppo in Syria than Baghdad at the time.

But the British coveted Mosul’s oil, while the French sought to maintain control of Syria, even though British forces had been the ones to take Damascus from the Ottomans during the war. A deal was struck that gave the British a mandate over Mosul and the French colonial rights over Syria and Lebanon. The Europeans reneged on assurances they had given Arab allies during World War I that they would allow an independent Arab state to emerge. Instead, the political map of the Middle East was shaped by British and French colonial concerns and “Sykes-Picot” became short-hand for a toxic legacy of foreign meddling and domination.

The integration of Mosul into the other vilayets to the south, writes Middle East historian Juan Cole, compelled the “British to depend on the old Ottoman Sunni elite, including former Ottoman officers trained in what is now Turkey. This strategy marginalized the Shiite south, full of poor peasants and small towns, which, if they gave the British trouble, were simply bombed by” the British air force.

The template was set. Iraq, under the rule of a British-installed monarchy, achieved independence in 1932. In a matter of decades, the monarchy would be abolished and, after a series of coups, the authoritarian Baathist party of Saddam Hussein took over. A cadre of Sunni political and military elites went on to dominate a majority Shiite nation until the 2003 U.S. invasion.

The Turkey that never was

In 1920, in its last session, a defeated Ottoman parliament declared in a six-point manifesto the conditions on which it would accept the end of World War I following the armistice in 1918. There are differing versions of the proposed borders of a shrunken Turkish state that the nationalists in the Ottoman parliament put forward — one of them is reproduced above. Some areas indicated would be allowed to hold referendums; others were considered integral Turkish territory. As you can see, though, Mosul was very much part of this vision.

Instead, the Ottoman court signed the withering Treaty of Sevres in 1920, which would have seen what’s now Turkey carved up into various spheres of influence controlled by the West, Kurds, Armenians and others. That never came to pass: Turkish nationalists in the Ottoman army mobilized and eventually forced out foreign forces. In the 1923 Treaty of Lausanne, Turkey’s modern borders were set.

Mosul, though, was a sticking point, with Turkish nationalists laying claim to it and demanding Britain hold a plebiscite in the region that’s now northern Iraq. That didn’t happen, and after some fitful politicking at the League of Nations, Turkey and Britain eventually agreed to an arrangement in 1926 where Ankara dropped its claim to Mosul and the nearby cities of Kirkuk and Sulaimanyah in exchange for a portion of the region’s oil revenues over the next 25 years.

This history has bubbled up once more in the wake of the Mosul offensive: Turkish President Recep Tayyip Erdogan, adamant that his country’s forces play a role in the mission, invoked the 1920 document when justifying his nation’s right to be “at the table.” Officials in Baghdad were not impressed.

The chaos of the moment

And here’s the current state of play. Mosul is now at the center of a regional conflagration: It’s occupied by an extremist Sunni organization that rose to power as the Iraqi and Syrian states imploded. An Iraqi government backed by pro-Iranian Shiite militias is seeking to retake the city with the aid of Kurdish peshmerga forces, whose fighters are well aware of their own people’s long, bitter quest for an independent Kurdish homeland. And it’s eyed by Turkey, wary of the growing aspirations of Kurdish nationalists in the region and eager to reassert its own influence in a part of the world that was once under its sway.