New Delhi, Jan 1 : Israel has withdrawn five military brigades from Gaza as it transitions into the third phase of operations in the enclave, media reports said. As per the reports the Institute for the Study of War -- a policy research organisation focused on US national security -- said that the third phase will include the end of major combat operations. 'A reduction in forces in Gaza, the release of reservists, a transition to targeted raids, and the establishment of a security buffer zone within the enclave,' Study of War said, as quoted by media reports. It said that an unidentified Israeli intelligence officer has said that most of Hamas' command structure is gone and that Hamas is no longer operating as a military organisation. Israel launched a ground offensive inside Gaza on October 27 after Hamas attacked Israel in a surprise attack on October 7 in which 1200 Israelis were killed and over 200 were taken hostage. Since the outbreak of hostilities, at least 21,822 Palestinians have been killed mostly being children and women while 56,451 Palestinians have been injured. /IANS