When U.S. and Iraqi troops invade the Islamic State group’s stronghold in Mosul, a big part of the battle may occur underground.

The massive military operation, expected to begin in October, will be complicated by a network of tunnels beneath the city. These labyrinths will offer a key tactical advantage to the ISIS fighters who are entrenched in Mosul.

“Daesh are very keen to build tunneling networks because it helps them to maintain security and preserve their lives a little bit longer whenever clearing operations begin,” said Air Force Col. John Dorrian, a top spokesman for U.S. troops in Iraq. Daesh is another name for ISIS. “In a city the size of Mosul,” he added, “that’s going to, you know, slow things down and make it a complicated task.”

Tunnels pose a vexing problem for the U.S. military, which lacks reliable technology to detect and map the subterranean pathways. They’ll make small-unit operations extremely difficult.

If, for instance, the passageways are built with zigzags, small-arms fire will be ineffective. They could be booby trapped to kill intruders. Oxygen can run short. Traditional communications devices might not function well. Medical evacuation will be slowed if walls collapse or if small exit points are covered by enemy fire.

Read More- Military Times

Image courtesy of AP