Effort to take Mosul throws up a crucial question for western policy
"The final authority must be in the hands of the Sunnis," wrote the British intelligence official. "Otherwise you will have a… theocratic state, which is the very devil."
The official in question was Gertrude Bell, the explorer and civil servant who, in 1921, sat down at her desk in Baghdad to draw the border of what is now modern-day Iraq.
Ms Bell's remarkable life story - the subject of a Werner Herzog film last year - was told again last week in 'Letters From Baghdad', an excellent documentary screened as part of the British Film Festival.
But while her admiring biographers dwell on her erudition and foresight, they gloss over her big misjudgement: the idea that handing power to Iraq's minority Sunni sect instead of the Shia majority would keep the peace.
And Ms Bell's story is being revisited on screen just as the West faces the question of whether it will tear up the map she drew.
For the past few months, the Western-backed Iraqi military has been preparing for its biggest battle yet against Isil - the retaking of Mosul, a city of 1.5 million captured by the terrorist group in 2014.
Now it is in motion, but trouble has been brewing.
Against Baghdad's wishes, Turkey has tried to step up its involvement in the offensive, setting off a row between Baghdad and Ankara.
The US, whose planes are backing up the offensive, insisted that the plan to take Mosul would not change.
But even as it begins, no one knows what might happen to the city afterwards.
This might seem very far away from the desert adventures and political dinner parties of Ms Bell's Baghdad.
But behind the effort to take Mosul lies a crucial question for western policy: are the US and its allies still committed to defending those lines Ms Bell drew on a map decades ago, which placed Mosul, a Sunni-majority town, inside a Shia-dominated Iraq?
Or will they abandon them in favour of a new map populated by sectarian nations like "Sunni-stan" and "Shiite-stan"?
The creation of Iraq was a typical British attempt at nation-building.
Having promised its inhabitants independence and seized Iraq from the Ottoman Empire in World War I, Britain first made a disastrous and bloody attempt to rule directly (against Ms Bell's advice) and then (on her recommendation) imported a friendly Sunni from Arabia and installed him as king.
The Sunni elites, in Ms Bell's view, would build a sophisticated, pro-British and non-theocratic state.
Ms Bell was speaking with some authority, having spent years travelling and making contacts among Sunni Arab tribes, but also hubris.
She had had limited contact with Shiite groups, whom she dismissed as backwards, and misplaced faith in King Faisal, whom she helped to crown.
The West has spent decades defending the European-made borders of the Middle East.
But since Syria fell apart and Isil stormed across the region, support for the creation of a new Sunni-ruled, Sunni-inhabited state, dubbed "Sunni-stan", has been growing on the American Right.
Late last year, John Bolton, George W Bush's ambassador to the UN, penned a 'New York Times' article arguing that Nato should support a 'Sunni-stan' because "Iraq and Syria as we have known them are gone".
A piece published in the influential US magazine 'Foreign Affairs' made a similar case, as did an article this week by former USAID official Joshua Cohen.
If an anti-Isil coalition succeeds in retaking Mosul, these musings could move from theory to live debate.
Mosul and its residents are pawns in this power struggle.
Iraq's Shia militias see an opportunity to depopulate the city of its mostly Sunni population and gain territory.
Mr Erdogan, on the other hand, says he wants to protect Sunni Turkmen in the region, but also sees a chance to create a pro-Turkish Sunni sphere of influence in Iraq, giving him greater room for manoeuvre. (© Daily Telegraph London)