Last stand for IS in Iraq
The battle to liberate the Iraqi city of Mosul from Islamic State began in earnest in the early hours of yesterday.
The Iraqi army has been ordered to evict the terror group from its last major stronghold in the country, Haider al-Abadi, the Iraqi prime minister, announced on state TV.
The offensive is a joint operation by more than 30000 troops of the Iraqi army, and Kurdish Peshmerga and Shia paramilitary forces, which are pushing in on the city from three sides.
About 8000 jihadists are believed to be in Mosul, which has been under IS control since the militants swept through northern Iraq in 2014.
The city is important strategically, because of its proximity to Syria and being on the supply route to Turkey, as well as symbolically.
In recent weeks the Iraqi army and its allies have gradually advanced on Mosul and the US-led coalition has been bombing IS targets.
There are fears that IS is using some of the 1.5million people of the city as human shields. The terrorists have threatened to kill anyone caught trying to flee Mosul.
The launching of the operation is only the opening shot of a battle that is likely to be the longest and most complex yet in the fight against the terror group.
What is Mosul and why is it important?
Mosul, the main industrial city in northern Iraq, is a hub in trade with Turkey and Syria.
About 400km north of Baghdad, it is also significant because of its oil fields.
It has traditionally had a diverse population. At the start of the this century most of its inhabitants were Arab Sunni Muslims living alongside Assyrian Christians, Kurds, Yazidis, Turkmens and other minorities.
Mosul is IS's last bastion in Iraq and is where the group has its roots. Abu Bakr al-Baghdadi, its Iraqi leader, announced the formation of his group's caliphate in the city.
Some analysts say the recapture of Mosul would spell the end for IS in Iraq and the group would effectively be confined to Syria, where it is also under pressure and losing territory.
Who is involved?
The offensive is being waged by a complicated combination of regional and international forces with competing objectives.
Although the rival forces share an immediate common goal of liberating Mosul, in the long term they could well be in conflict over what happens next.
Iraq's government wants to reassert control over Mosul.
However, Kurdish forces want to expand their semi-autonomous state, which skirts Mosul. They say they will keep any land they capture.
The operation is complicated further by Turkey's insistence on having some of its own troops on the frontline.
Turkey has a historical claim to the city from the days of Ottoman rule and wants a say in its future governance.
Baghdad has objected, however, accusing Ankara of wanting to use the Sunni tribal force as a proxy in support of its own interests.
What role is Britain playing in the battle for Mosul?
Mosul has been the focus of Britain's war against IS since the liberation of Fallujah last year.
Britain's effort, code-named Operation Shader, has included eight RAF Tornado and six Typhoon jets flying armed reconnaissance missions and making air strikes in support of the forces closing in on the city.
By the middle of this month warplanes based at RAF Akrotiri, in Cyprus, and Reaper drones flying from Kuwait had carried out more than 200 strikes around the city, second in number only to those of the Americans.
RAF spy planes based in Cyprus have spent weeks mapping enemy positions and movements, and intercepting communications.
Small groups of British SAS special forces soldiers are advising Kurdish Peshmerga fighters and helping co-ordinate air strikes.
Away from the frontline, about 500 British soldiers at bases including al-Asad, Taji, Besmaya and Erbil have been training Iraqi and Kurdish troops in battlefield medicine, how to deal with IS bombs and basic infantry drills.
Instructors have spent months preparing the Iraqi forces to breach IS minefields thought to surround the city.
How long will the battle last?
Al-Abadi said he hoped Mosul would be liberated by the end of the year. But even conservative estimates suggest that it could take at least three months of street-to-street fighting .
What about Mosul's residents?
There are fears for the 1.5million residents of the city. Those trying to escape the fighting have to run a gauntlet of sniper fire, landmines and trenches filled with burning oil.
The Iraqi Air Force dropped thousands of leaflets on Mosul at the weekend to warn residents, who have been cut off from the internet and phones, of the imminence of the offensive.
Citizens are also worried that the Popular Mobilisation Unit, a strong paramilitary group that the government has relied on in the fight against IS, could take advantage of the chaos after the liberation to inflict sectarian reprisals on local Sunnis as they have in other towns.
Aid agencies are also warning that the battle is likely to spark a crisis, warning that up to a million people might be displaced by the fighting as winter sets in.
More than 100,000 people have already fled to about half a dozen tent cities. The UN is scrambling to build more, but if the numbers reach the highest predictions the crisis could be catastrophic.
WHAT HAPPENS AFTER MOSUL
It has been a dramatic weekend for Islamic State. The symbolic town of Dabiq in Syria fell, and the ground assault on Mosul, their capital in Iraq, began.
This likely heralds the beginning of retrenchment for the group, as they find themselves in retreat.
But w e must lay the groundwork to properly eradicate IS , rather than let Iraq sink into sectarianism as it did in the past.
A major concern is what will happen to the mass of foreign fighters who will be suddenly left without a home.
Rudderless but with revolutionary purpose, this group will present a menace to security officials around the world for years to come.
In terms of the numbers of fighters in Syria and Iraq, it is hard to find a precedent.
The closest is the war in Afghanistan in the 1980s, when the mujahedeen battled the Russians. This produced the beginnings of al-Qaeda, and created a cadre who sensed an opportunity to overthrow regimes in their home countries.
The speed and nature of the flow of fighters that went to Syria and Iraq to fight IS is different. But there's a high probability of a threat .
There is an obvious risk of directed cells. IS has shown a capacity to send individual fighters back hidden among refugees coming to Europe.
This will likely continue, with a mix of individuals returning home feeling that their fighting days are over alongside individuals tasked with launching attacks.
Preventing any plots emerging now or in the future will be a major concern to European authorities for some time.
In addition, a s IS is pushed back from Mosul, there is the possibility that attention will drop off once again. The last time the west seemed to score a victory in Iraq, the allies lost attention and withdrew.
The result was a sectarian mess in Iraq that provided the groundwork for IS, creating the environment from which it was able to grow. - ©The Daily Telegraph