From suicide bombers and executioners to weapons experts and religious police, the Islamic State uses a complex network of militants to wage its terror war in the Middle East.
To differentiate the various roles within its hierarchy, it has, perhaps more than other military organisation, sought to assign corresponding uniforms for each unit.
These, say anti-ISIS activists who live in the shadows in the terror group's de facto capital Raqqa in Syria, can be broken down into several categories, each as sinister as the next.
The first, and perhaps the most common, is known as the 'Afghani robe' – a camouflage green outfit worn by fighters on the frontline or while manning checkpoints.
This is often accompanied by a beige ammunition belt and black balaclava.
One of the most distinctive uniforms – the all-black jacket and trousers with balaclava and black ammunition belt – is assigned to the suicide bombers.
According to activists Raqqa Is Being Slaughtered Silently (RIBSS), it is also worn by the 'princes of ISIS' – or senior figures – in battle and for those conducting reconnaissance missions.
A sandy-coloured desert camouflage version, meanwhile, is assigned to the terrifying special units responsible for the group's barbaric executions.
They were most notably seen in video of the horrific murder of a captured Jordanian pilot who was burned alive earlier this year.
Other senior executioners, however, like the British extremist known as Jihadi John, also to wear head-to-toe black robes.
A similar all-black outfit, with a black sweater and usually without the ammunition belt, is worn by fanatics during parades, as seen when they captured the Syrian city of Raqqa last year and several other town and villages since.
A further variation is given to militants responsible for training the next generation of recruits at its terror camps, consisting of a pair of black trousers with a long beige jacket.
Yesterday, it emerged that US intelligence fears nearly 30,000 foreign fighters from more than 100 countries have travelled to Iraq and Syria since 2011, many of them to join the Islamic State.
The number, which reportedly includes many westerners – among them possibly 250 Americans – represents a doubling of last year's US assessment.
In its latest attack, the group today claimed responsibility for a car bomb blast in central Baghdad that killed four people and wounded 11 others.
By Simon Tomlinson
