While the Iraqi army and popular mobilization forces wage bloody battles to liberate Tikrit from the Islamic State (IS), the terrorist group is  preparing to protect Mosul in anticipation of the next battle.

Mosul residents are expecting a huge battle involving the international alliance’s air force — and perhaps US ground forces — to liberate the IS stronghold. The organization’s militants have been digging trenches, erecting a high wall and taking other measures that can no longer go unnoticed by Mosul citizens.

A Mosul resident who chose to use the pseudonym Sabah al-Ali told Al-Monitor, “For weeks, large vehicles have been working on digging a trench around the city.” He said that the trench is about 2 meters (6.5 feet) wide and over 1.5 meters (5 feet) deep, extending over long distances from the city's west and south, about 10 kilometers (6 miles) from the nearest inhabited area.

Ali said that digging such a huge trench is a massive project requiring laborious efforts. For that reason, IS agreed to pay a contractor $4,000 for each kilometer of trench.