Forces operating in Mosul theatre

A wide array of Iraqi and international forces are involved in the operation to retake Mosul from the Islamic State jihadist group, which overran the country's second city in 2014.

These are the main forces battling the estimated 4,000-7,000 IS fighters in and around Mosul:

Counter-Terrorism Service

The CTS is an elite Iraqi special forces unit that has spearheaded assaults in most key battles against IS. It is fighting toward Mosul from the east.

Rapid Response Division

The CTS's interior ministry counterpart that has developed into a key assault force in Iraq's war against IS. It is advancing on Mosul from the south.

Army

The army has begun playing a more successful role in operations against the jihadists since it was revitalised by US-led training after several of its divisions collapsed during the IS offensive two years ago. Soldiers are fighting on the northern, eastern and southern approaches to Mosul.

Police

Includes paramilitary federal police and provincial police forces. Many Iraqi police forces have played roles more akin to those of soldiers in the war against IS. They are operating on the southern front.

Hashed al-Shaabi

An umbrella organisation created in 2014, which includes a dizzying collection of paramilitary forces who vary widely in skill and in the degree to which they are actually under government control.

The main groups are Iranian-backed Shiite militias, including Ketaeb Hezbollah, Asaib Ahl al-Haq and Badr. The Hashed has played a major role in the anti-IS fight in Iraq but forces within it have also carried out abuses.

It also includes Sunni tribal forces sometimes referred to as "tribal mobilisation" or "national mobilisation".

Hashed forces aim to retake the town of Tal Afar to the west of Mosul and cut jihadist supply lines to Syria, but are fighting south and southwest of the city for now.

Kurdish forces

The peshmerga are the armed forces of Iraq's autonomous Kurdish region. They nominally answer to the federal government but in practice operate independently, battling IS along a long front in the country's north.

Forces from Iran's Kurdistan Freedom Party (PAK) are embedded in some peshmerga operations. It is separate from other Iranian Kurdish rebels groups that have also been active on the Iraqi side of the border such as the Kurdistan Democratic Party of Iran (KDPI) and the Party of Free Life of Kurdistan (PJAK). The Turkish Kurdistan Workers' Party (PKK) may also be involved in the Mosul operation.

Kurdish forces are operating north and east of Mosul.

US-led coalition

A US-led international alliance is carrying out air strikes against IS in Iraq and Syria, and providing training, arms and equipment to forces opposing the jihadists.

There are more than 7,500 coalition military personnel deployed in Iraq, over half of them from the United States.

Most are in advisory or training roles, but special forces soldiers who have fought the jihadists on the ground have been deployed and coalition forces near Mosul have also targeted IS with artillery.

Iranian advisers

Qassem Soleimani, the commander of Iran's Revolutionary Guards foreign operations wing, has been repeatedly pictured in Iraq during the war.

Turkish troops

Deployed at a base near Mosul from which they have carried out artillery strikes against IS. Turkish troops are also present inside Iraq's autonomous Kurdish region.

The federal government has demanded their withdrawal, with the prime minister vowing that they will not take part in the operation to recapture Mosul, but Turkey has declined to do so.