Lifeline to deathline: Gaza's tunnels

Israel's military texted reporters Monday, saying Hamas militants tried and failed to ambush Israeli soldiers.

Those militants emerged from below, spring the attack from one of the many tunnels that run under Gaza and into Israel.

Using tunnels has been the tactic of choice for under-funded, out-manned, and out-gunned enemies for thousands of years. One historian says Gazans used tunnels back in the days of the siege of Alexander the Great.

Hamas hopes these underground channels, once used for smuggling goods from Egypt into Gaza, can now be used to export death from Gaza into Israel.

CNN's Jake Tapper examines why destroying this spindly subterranean infrastructure is now priority number one for the IDF.