What Is Hamas, the Palestinian Militant Group Behind Terrorist Attacks on Israel?

Israel has declared war on Hamas and indicated that a long military campaign to defeat the Islamist group is on the horizon

On Saturday, the Palestinian militant group Hamas launched a massive surprise attack in southern Israel, killing hundreds of civilians and soldiers and taking at least 150 more as hostages.

In response, Israel declared war on Gaza — a Palestinian territory controlled by Hamas — and indicated that a long military campaign to defeat the Islamist militants is on the horizon.

As fighting continues, here's what to know about the group behind the deadly terrorist attack in Israel that escalated long-standing Israel-Palestine tensions.

What is Hamas?

Hamas is a Palestinian militant group designated as a terrorist organization by the United States. The group was founded in the 1980s and named after an Arabic acronym for the Islamic Resistance Movement. Hamas took power in Gaza in 2007 after violently seizing control from the Palestinian Authority, a government body run by the Fatah political party.

Hamas now rules the Gaza Strip, a 25-mile long territory between Israel, Egypt and the Mediterranean Sea. Gaza was historically under Egypt's control until the Six-Day War in 1967, after which Israel seized control of both the Gaza Strip and the West Bank. Since then, the regions have been the source of conflict for Israelis and Palestinians.

Currently, Israel controls all access into the Gaza Strip and restricts the import of goods there, but Hamas acts as the area's de facto government. Hamas is known for its brutal rule, which has historically resulted in kidnappings, rocket attacks and suicide bombings.

Members of Hamas say their primary goal is to free Palestinians from occupation and reclaim large parts of Israel, though that would mean destroying Israel, a Jewish nation, and replacing it with an Islamic state.

The group is financially backed by Iran, according to the Council on Foreign Relations, which says that the group rules in an authoritarian manner, repressing the Gazan media and political opposition as well as civilian activism on social media.

Where did Hamas attack?

The Oct. 7, 2023, attacks saw Hamas launch several thousand rockets into southern and central Israel, hitting cities as far north as Tel Aviv and on the outskirts of Jerusalem. These attacks are rare due to Israel's sophisticated Iron Dome missile defense system.

Roughly one hour after the rocket attacks began, Hamas militants breached the heavily defended Gaza border by land, sea and air, infiltrating nearly two dozen southern Israeli towns and taking civilians and soldiers hostage.

Related: Israeli Music Festival Survivors Recount Mass Casualty Hamas Attack: ‘A Trauma Like I Could Never Imagine’

At least 900 people have died and 2,500 have been wounded since the surprise attacks, Israel Defense Forces international (IDF) spokesperson Lt. Col. Jonathan Conricus told CBS News. There are reportedly over 150 Israelis being held hostage in Gaza, according to The New York Times, including U.S. citizens.

The IDF also reported that more than 3,200 rockets had been fired on Israel from Gaza.

That the attacks began in the early morning on Saturday, Oct. 7 — both the Jewish Sabbath and an important Jewish holiday — was no doubt intentional.

Related: Israeli Defense Minister Calls for ‘Complete Siege’ of Gaza Strip Two Days After Hamas' Surprise Attack

Why did Hamas attack?

Hamas leaders have said the group attacked in retaliation for Israel’s occupation of the West Bank which, like the Gaza Strip, has been a focus of the Israel-Palestinian conflict for more than a hundred years.

Members of the group have also cited recent Israeli police raids on a Jerusalem mosque as well as the detention of thousands of Palestinians in Israeli jails as reasons for the attack.

Muhammad Deif, the leader of the military wing of Hamas, said in a recorded message that the attack came so that “the enemy will understand that the time of their rampaging without accountability has ended," The New York Times reports.

How has Israel responded?

The attack prompted Israeli Prime Minister Benjamin Netanyahu to say that the country is “at war" during a televised speech broadcast Saturday. Meanwhile, Israeli Defense Minister Yoav Gallant announced “a complete siege on Gaza,” blockading the Palestinian territory from amenities like electricity, food, water and gas.

In retaliation, Israeli defense forces have also struck at least 653 Hamas targets.

Netanyahu has said that the “first phase” of Israel’s response has been completed, though it remains unclear whether Israel plans to invade Gaza in retaliation.

Related: Israeli Father Recalls Panicked Phone Call Before His Wife and 2 Young Girls Were Kidnapped and Taken to Gaza

Following Saturday's attack, leaders of the U.S., U.K., France, Germany and Italy issued a joint statement condemning Hamas.

“All of us recognize the legitimate aspirations of the Palestinian people," the statement read. "But make no mistake: Hamas does not represent those aspirations, and it offers nothing for the Palestinian people other than more terror and bloodshed.”

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What happens now?

As Israel continues to deal with the fallout from the attacks, Hamas has vowed that it will kill an Israeli hostage for every time Israel bombs a Palestinian home without warning, Al Jazeera reports. At least some of those hostages may be American.

In a statement released Monday, Biden, 80, said that at least ten Americans, “many of whom made a second home in Israel,” were killed after Hamas launched its surprise terrorist attack.

Related: Joe Biden Says Americans ‘Likely’ Among Hostages Taken by Hamas During Surprise Attack

“It’s heart-wrenching,” he said in a statement. “My heart goes out to every family impacted by the horrible events of the past few days. The pain these families have endured, the enormity of their loss, and the agony of those still awaiting information is unfathomable.”

Biden said many more Americans were still unaccounted for and the White House believes that some are being held hostage by Hamas.

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