Israel has formally declared war on Hamas after an unprecedented attack involving thousands of rockets and incursions past Israel's borders.
Armed Hamas fighters on Saturday blew up parts of Israel's highly fortified separation fence and strode into Israeli communities along the Gaza frontier, terrorising residents and trading fire with Israeli soldiers. More than 1000 people have been killed and thousands wounded on both sides.
Here's what you need to know about the conflict so far.
Hospitals will be 'mass graves' as Gaza crisis worsens: doctor
What has happened?
The Israel Defence Forces said around 2200 rockets were fired at Israel. Hamas put the figure at 5000. To put that in context, some 4000 rockets were fired from Gaza into Israel during the 50-day war between the two sides in 2014.
Hamas military commander Muhammad Al-Deif called the operation "Al-Aqsa Storm" and said that the assault on Israel was a response to attacks on women, the desecration of the Al-Aqsa mosque in Jerusalem and the ongoing siege of Gaza.
Hamas said it captured Israeli soldiers, posting videos of soldiers it allegedly captured on its social media accounts. Videos geolocated and authenticated by CNN suggested that at least one Israeli soldier was taken prisoner by the group.
"There are hostages and prisoners of war that Hamas took. There are also deaths among IDF soldiers. We don't have an exact number yet – we are at war," said IDF Spokesperson Rear Admiral Daniel Hagari.
Hamas said in a statement Sunday that its fighters were still present in southern Israeli cities, and that the group was supporting them with rocket fire in the cities of Ofakim, Sderot, Yad Mordechai, Kfar Aza, Be'eri, Yated, and Kissufim.
How has Israel responded?
In response to the attack, Israel launched "Operation Swords of Iron," striking a number of targets in the Gaza Strip. Prime Minister Benjamin Netanyahu said Israel's response to the Hamas incursion will "exact a huge price" from the group.
The IDF urged civilians in Gaza to leave their residential areas immediately for their safety as Israeli military operations continued to target Hamas.
IDF spokesperson Lieutenant Colonel Richard Hecht told CNN on Saturday that "tens of thousands" of Israeli reservists have also been called up to help.
He said Israel is "ready in the north" in case there are attacks from Lebanon or Syria.
Inside Gaza, the roar of Israeli warplanes could be heard followed by loud explosions and rising plumes of black smoke.
By nightfall, Israeli airstrikes on the territory had killed hundreds and wounded thousands.
At least 313 people were killed over 24 hours, including at least 20 children, the Palestinian Ministry of Health in Gaza said Sunday. Another 1990 were injured, it added.
An Israeli official told CNN early Sunday morning that 350 people were killed in Israel. The IDF published the names of 44 soldiers it says were killed in the attack.
On Sunday, the IDF said it struck 426 targets in Gaza, including 10 towers it said were used by Hamas.
In the north, Lebanon's Iran-backed Hezbollah group claimed responsibility for targeting three Israeli sites in an area known as Shebaa Farms using missiles and artillery. The area is considered by Lebanon as Israeli-occupied. Israel responded by firing artillery.
And in the Israeli-occupied West Bank, seven Palestinians were killed by Israeli soldiers on Saturday when clashes broke out after the Israeli army blocked West Bank cities, according to the Palestinian Ministry of Health.
Did Israelis detect the attack ahead of time?
The shock that Israelis felt on Saturday morning — on Simchat Torah, one of the most joyous days of the Jewish calendar — recalled the surprise of the 1973 Mideast war.
Practically 50 years earlier to the day, a full-scale Egyptian-Syrian attack on a Jewish holiday quickly turned into a disaster for an unprepared Israeli military.
Then, as now, Israelis had assumed that their intelligence services would be able to alert the army to any major attack or invasion well in advance. That colossal failure still haunts the legacy of then-Prime Minister Golda Meir and helped bring down the lengthy rule of the once-dominant Labor Party.
Now, the question of how the militants were able to stage such a huge and coordinated attack — which has already killed more Israelis than any single assault since the second Palestinian uprising two decades ago — without triggering Israeli intelligence concerns has already presented a major challenge to Netanyahu's ultranationalist government.
The government's supporters had expected Netanyahu and hard-line ministers with a history of anti-Arab rhetoric like National Security Minister Itamar Ben-Gvir to take a particularly belligerent stance against the Palestinians and respond more forcefully to threats from militants in Gaza.
As political analysts lambast Netanyahu over the failure, and the casualty count climbs, Netanyahu risks losing control of both his government and the country.
How was Hamas able to carry out the assault?
Hamas claimed its fighters took several Israelis captive in the enclave, releasing gruesome videos of militants dragging bloodied soldiers across the ground and standing over dead bodies, some of them stripped to their underwear. It said senior Israeli military officers were among the captives.
The videos could not immediately be verified but matched geographic features of the area. Fears that Israelis had been kidnapped evoked the 2006 capture of soldier Gilad Shalit, whom Hamas-linked militants seized in a cross-border raid. Hamas held Shalit for five years until he was exchanged for over 1000 Palestinian prisoners held by Israel.
In a dramatic escalation unseen in decades, Hamas also sent paragliders flying into Israel, the Israeli military said. The brazen attack recalled a famous assault in the late 1980s when Palestinian militants crossed from Lebanon into northern Israel on hang-gliders and killed six Israeli soldiers.
The Israeli army belatedly confirmed that soldiers and civilians were taken hostage in Gaza, but refused to provide further details.
How did the two sides get here?
Tensions between Israel and the Palestinians have existed since before the nation's founding in 1948. Thousands of people on both sides have been killed and many more injured in the long-simmering conflict between the two sides over decades.
Violence has been particularly heightened this year. The number of Palestinians – militants and civilians – killed in the occupied West Bank by Israeli forces is at its highest in nearly two decades. The same is true of Israelis and foreigners – most of them civilians – killed in Palestinian attacks.
Israel and Hamas have been involved in armed conflict dating back as early as the 1987 First Palestinian Intifada, or uprising, against Israel's occupation of the Gaza Strip and the West Bank.
Israel captured Gaza from Egypt in a 1967 war, then withdrew in 2005. The territory, home to some two million Palestinians, fell under Hamas' control in 2007 after a brief civil war with Fatah, a rival Palestinian faction that is the backbone of the Palestinian Authority.
After Hamas seized control of Gaza, Israel and Egypt imposed a strict siege on the territory, which is ongoing. Israel also maintains an air and naval blockade on Gaza.
Before Saturday's operation, the last war between Hamas and Israel was in 2021, which lasted for 11 days and killed at least 250 people in Gaza and 13 in Israel.
Saturday's assault occurred on the 50th anniversary of the 1973 war, when Israel's Arab neighbors launched a surprise attack on Israel on Yom Kippur, the holiest day in the Jewish calendar, on October 6, 1973.
Attack comes when Israeli society is divided
The eruption of violence comes at a difficult time for Israel, which is facing the biggest protests in its history over Netanyahu's proposal to weaken the Supreme Court while he is on trial for corruption.
The protest movement, which accuses Netanyahu of making a power grab, has bitterly divided Israeli society and unleashed turmoil within the Israeli military. Hundreds of reservists have threatened to stop volunteering to report for duty in protest at the judicial overhaul.
Reservists are the backbone of the country's army, and protests within the army ranks have raised concerns about the military's cohesion, operational readiness and power of deterrence as it confronts threats on multiple fronts. Netanyahu on Saturday called up "an extensive mobilisation of reserve forces."
What kind of cease-fire or resolution can be expected?
Israel and Hamas have fought four wars and exchanged fire numerous times since the Islamic militant group seized control of Gaza from forces loyal to the Palestinian Authority in 2007.
Cease-fires have stopped major fighting in past rounds of conflict but have always proven shaky.
Each agreement in the past has offered a period of calm, but the deeper, underlying issues of the conflict are rarely addressed and set the stage for the next round of airstrikes and rockets.
With its increased leverage in this round, Hamas is likely to push harder for concessions on key issues, such as easing the blockade and winning the release of prisoners held by Israel.
What is Hamas?
Hamas is an Islamist organisation with a military wing that came into being in 1987, emerging out of the Muslim Brotherhood, a Sunni Islamist group that was founded in the late 1920s in Egypt.
The word "Hamas" is itself an acronym for "Harakat Al-Muqawama Al-Islamia" – Arabic for Islamic Resistance Movement. the group, like most Palestinian factions and political parties, insists that Israel is an occupying power and that it is trying to liberate the Palestinian territories. It considers Israel an illegitimate state.
Its refusal to recognise Israel is one reason why it has rejected peace talks in the past. In 1993, it opposed the Oslo Accords, a peace pact between Israel and the Palestine Liberation Organisation (PLO).
The group presents itself as an alternative to the Palestinian Authority (PA), which has recognised Israel and has engaged in multiple failed peace initiatives with it. The PA is today led by Mahmoud Abbas and is based in the Israeli-occupied West Bank.
Hamas has over the years claimed many attacks on Israel and has been designated as a terrorist organisation by the US, the European Union and Israel. Israel accuses its archenemy Iran of backing Hamas.
Hamas was classified in Australia as a terrorist organisation in its entirety last year. Its paramilitary wing, the Izz al-Din al-Qassam Brigades, had been classed as terrorists in Australia since 2003.
Israel-Hamas war: What we know so far
Hamas militants crossed into Israel by land, sea and air in the early hours of Saturday morning. The militants infiltrated 22 towns and army bases. Civilians and soldiers were killed and taken hostage.
At least 700 people have reportedly been killed in Israel.
Israel formally declared war on Hamas on Sunday and have been pounding Gaza with airstrikes.
More than 400 Palestinians have reportedly died. Hamas has fired over 4000 rockets into Israel.
The Wall Street Journal today reported Iran helped Palestinian militants plan their shock assault. The US has ordered a large carrier strike force sail to the eastern Med.
