The Gaza tunnel network: A tactical edge for Hamas As Israel appears to prepare a ground invasion of Gaza, the Israeli military is looking closely at the so-called Gaza metro. This labyrinth of tunnels dug under Gaza was initially used to smuggle goods from Egypt. But today, it's set to become a huge tactical advantage for Hamas, who are using it to move fighters and weapons and hide Israeli hostages. Our Science and Tech editor Julia Sieger tells us more.