Because Hezbollah's fortified sites and underground facilities are resistant to airstrikes, they cannot be neutralized without a ground response. In turn, Hezbollah can use its weapons caches and strongpoints to challenge Israeli ground forces. In 2006, distributed caches of necessities gave fighters sufficient provisions to fight despite IAF interdiction of resupplies. The group had about 500–600 weapons caches in 2006. Some Hezbollah units continued to fire rockets onto Israel even from behind IDF lines. Following the 2006 war, Hezbollah was forced to abandon its bunkers and "nature reserves" south of the Litani River. The 2006 war caused a change in the region of Hezbollah's military infrastructure; prior to the war, Hezbollah was concentrated south of the Litani River, while following the war Hezbollah's defensive apparatus is mostly north of it. Despite abandoning most of their bunkers, Israeli intelligence says they have "very good intelligence," but not proof, that Hezbollah has built bunkers and "underground cities" in the UNIFIL zone in southern Lebanon.