Operation Al-Aqsa Flood was a major surprise offensive launched by Palestinian militant groups into southern Israel in October 2023.
2023 had seen the deaths of 247 Palestinians, 32 Israelis, and 2 foreign nationals in outbreaks of violence in the Israel-Palestine region, while Hamas and Israel negotiated a truce, mediated by Qatar, Egypt, and the United Nations on 29 September. At the same time, Saudi Arabia conducted normalization talks with Israel. However, Palestinian anger over the 5 April 2023 clashes on Temple Mount, home of the Al-Aqsa Mosque, continued to boil. Izz ad-Din al-Qassam Brigades leader Mohammed Deif planned a surprise offensive against Israel in response to the "desecration of the al-Aqsa Mosque", and, at 6:30 AM on 7 October 2023, a major invasion of Israel from Gaza began.
Hamas fired over 5,000 rockets from the Gaza Strip into Israel within a span of 20 minutes, striking Gedera, Herzliyya, Tel Aviv, and Ashkelon and killing at least five people. Deif called on "Muslims everywhere to launch an attack" as Palestinian militants opened fire on Israeli boats off the Gaza Strip and 1,000 Palestinian militants infiltrated Israel from Gaza using trucks, pickup trucks, motorcycles, bulldozers, and paragliders, achieving complete surprise. Black-clad terrorists massacred several Israeli civilians and soldiers in Sderot, while Palestinian militants took several Israeli captives from Be'eri, Netiv HaAsara, and other kibbutzim and brought them back to Gaza as hostages. The Palestinian militants captured Nahal Oz, Kfar Aza, Magen, and Sufa Beheri, as well as the Sderot police station and the Erez border crossing.
The attack coincided with the Jewish holiday of Simchat Torah, the Jewish sabbath, and the day after the 50th anniversary of the Yom Kippur War of 1973 (which began with an Egyptian and Syrian surprise attack on Israel). While the Palestinians issued the call, "If you have a gun, get it out" to Arabs living in Israel and called on Hezbollah, Syria, Iran, and Iraq to join the battle against Israel, Prime Minister Benjamin Netanyahu declared war on the terrorists. The Iron Dome air defense system was activated, 17 Hamas military compounds in Gaza were struck by fighter jets, IDF reservists were deployed in Gaza, the West Bank, and along the borders with Lebanon and Syria, the streets of Tel Aviv were locked down, residents of areas near the Gaza Strip were asked to stay inside, and the Yamam counterterrorism unit was deployed to southern Israel. 198 Palestinians were killed in Gaza and another 1,610 injured due to Israeli retaliatory strikes, while Netanyahu vowed that Hamas would "pay a price it has never known", telling Israel's citizens "we are at war - not in an operation, not in rounds - at war." Hamas promised "earth-shattering" retribution for Israeli attacks on Gaza, while Israel promised a much more devastating response against Hamas than had ever been conducted.
By the morning of 8 October 2023, Israel recaptured Sderot, and Israel's Security Cabinet issued a formal declaration of war on the terrorists and authorized a series of actions to bring about the destruction of both the military and governmental capabilities of Hamas and the PIJ. Israel cut off Gaza's electricity, of which 80% had been supplied by the Israel Electric Corporation. Overnight, Israel struck many targets in the Gaza Strip, while resolving two hostage situations and clearing 22 locations from Palestinian forces (rescuing 50 hostages in the process). Israel also evacuated residents living near the Gaza Strip in preparation for a ground war in Gaza. That same day, Hezbollah fired rockets and shells at the Shebaa Farms region, leading to Israeli retaliatory artillery and drone strikes. An Egyptian policeman also went rogue and attacked Israeli tourists and their Egyptian guides in Alexandria, killing two Israelis and one Egyptian before he was detained by the Egyptian police. By the morning of 9 October, the Al-Aqsa Martyrs' Brigades armed wing of Fatah called for lone wolves to "restore glory" of suicide attacks, raid settlements, and strike "with all force to end faltering Israel."
Israeli forces reclaimed Kfar Aza on 10 October, discovering the bodies of 40 babies and a total of 100 civilian victims; IDF soldiers claimed that Hamas attackers had cut off the heads of babies during their shock attack. The IDF also launched airstrikes on the al-Daraj, al-Furqan, and Port of Gaza neighborhoods of Gaza, while striking the Rafah border crossing between Gaza and Egypt. The home of Hamas military chief Mohammed Deif was also struck, killing his father, brother, and at least two other relatives. On 11 October, Israeli warplanes destroyed several buildings of the Islamic University of Gaza that were being used as weapons factories and training grounds. That same day, Israel formed an emergency war government, including former Defense Minister Benny Gantz as part of Netanyahu and Defense Minister Yoav Gallant's war cabinet. Netanyahu's comparisons of Hamas to ISIL coincided with the discovery of an ISIL flag left behind by Hamas militants at the kibbutz of Sufa; ISIL flags were also found on the bodies of several terrorists. By 12 October, the Israelis' cutting off of electricity and water from Gaza resulted in Gaza hospitals running out of available fuel powering generators. Israel demanded that Hamas release all Israeli hostages in exchange for the blockade being lifted. Meanwhile, as clashes between the IDF and Hezbollah continued on the border with South Lebanon, Israel launched attacks on the international airports of Damascus and Aleppo, causing Syrian air defenses to be activated. By 13 October, only sporadic fighting continued in Israel due to a handful of Hamas militants holing up in devastated kibbutzim, while Israel prepared a major ground assault on Gaza.