<section begin=Lead /> In the Gaza Strip, the governing authority Hamas developed a sophisticated network of military tunnels. The tunnel system branches beneath many Gazan towns and cities, such as Khan Yunis, Jabalia and the Shati refugee camp. The internal tunnels, running some dozens of kilometres within the Gaza Strip, have several functions. Hamas uses the tunnels to hide its arsenal of rocketry underground, to facilitate communication, to permit munition stocks to be hidden and to conceal militants, making detection from the air difficult. Hamas regards their tunnel system as a defensive structure designed to place obstacles against Israel's powerful military arsenal, to protect its people, and engage in counter-strikes against the IDF when Gaza is attacked.