A vast network of tunnels used for smuggling and warfare purposes exists under the Gaza Strip. The underground tunnel network allows Hamas and other militant groups to store and shield weapons, gather and move underground, communicate, train, launch offensive attacks, transport hostages, and retreat without being detected by Israeli or Egyptian authorities. This network of tunnels is colloquially referred to as the Gaza metro.‌ According to General Hassan Hassanzadeh, the commander of the Islamic Revolutionary Guard Corps (IRGC) forces in Tehran, there are more than 500 kilometers of tunnels.

Tunnel warfare is using tunnels and other underground cavities in war. It often includes the construction of underground facilities in order to attack or defend, and the use of existing natural caves and artificial underground facilities for military purposes. Tunnels can be used to undermine fortifications and slip into enemy territory for a surprise attack, while it can strengthen a defense by creating the possibility of ambush, counterattack and the ability to transfer troops from one portion of the battleground to another unseen and protected. Also, tunnels can serve as shelter from enemy attack.