18:26 12 June 2014 by Debora MacKenzie
Iraq has blazed its way back onto the world's front pages in the past 48 hours, with the seemingly sudden capture of the cities of Mosul and Tikrit by an extremist group. The group seems to be targeting the region's rivers: its main geostrategic vulnerability. It now controls the upper reaches of both the Tigris and Euphrates in Iraq.
The Islamic State of Iraq and Syria (ISIS) considers itself the true government of a region stretching from Israel to Iraq. It has been among the rebels fighting Syrian president Bashar al-Assad, and controls the territory in eastern Syria around Deir al-Zour.
Despite the apparent suddenness, ISIS's assault on Iraq has been brewing for six months. Last January, ISIS started fighting its way from Syria down the Euphrates river into Iraq. In May it captured the town of Fallujah, the scene of bloody fighting during the 2003 US-led invasion of Iraq. This week, ISIS captured Iraq's second-largest city Mosul, on the Tigris river, then advanced down the Tigris to the town of Tikrit, and beyond it to the Shiite holy town of Samarra. Both Samarra and Fallujah are within striking distance of the capital Baghdad.
It is not clear at the time of writing whether ISIS will launch a military attack on Baghdad, or even if it could take the heavily armed city in a pitched battle.
Choke points
But it may not need to. Iraq is ancient Mesopotamia, the once-fertile floodplain of the Tigris and Euphrates that cradled the first human civilisation. The rivers remain crucial to the farming on which most Iraqis depend, according to a report by the International Centre for Agricultural Research on the Dry Areas, which was once based in Aleppo, Syria, but has now decamped to Amman in Jordan to avoid fighting.
ISIS now controls several major dams on the rivers, for instance at Haditha and Samarra. It also holds one 30 kilometres north of Mosul that was built on fragile rock and poses a risk of collapse. It holds at least 8 billion cubic metres of water. In 2003, there were fears Iraqi troops might destroy the dam to wipe out invading forces. US military engineers calculated that the resulting wave would obliterate Mosul and even hit Baghdad.
ISIS has already used water as a weapon, in a smaller way. In late April ISIS stopped flow through the relatively small Nuaimiyah dam on the Euphrates in Fallujah, reportedly with the aim of depriving Baghdad and southern Iraq of water. It could also have been to block military approaches to the town.
Instead, the river backed up and poured into an irrigation canal, flooding the town of Abu Ghraib and dozens of surrounding villages over 200 square kilometres. Five people died, and 20,000 to 40,000 families fled to Baghdad. The water may have permanently damaged soils, and deprived farmers downstream of vital irrigation water at a critical time of year. Southern Iraq is mainly populated by Shiite Muslims, to whom ISIS and its Sunni allies are opposed.
