Gaza is covered in plumes of smoke as Israeli bombardment enters day four. In the enclave, blockaded by land, air, and sea, a labyrinth of tunnels is Gaza’s lifeline, bringing in everything from food and weapons to fuel. The tunnels are also Hamas’ outposts, acting as storage and essential portals. Reports suggest that the Israeli military has targeted the tunnels in northwestern Gaza. Tunnels were attacked by deploying powerful bombs known as bunker busters. Watch this report to understand what bunker busters are and how they work.