Israeli Prime Minister Benjamin Netanyahu declared war on the Palestinian militant group Hamas after it launched a surprise attack over the weekend. Hundreds of people have died on both sides, including Palestinian children, and dozens of Israelis have been taken hostage.

On Monday, Israel ordered a "complete siege" of Gaza after launching several airstrikes from land and sea into the strip, an area of 140 square miles, from which the 2.3 million people are unable to flee. "There will be no electricity, no food, no fuel," Israeli Defense Minister Yoav Gallant said. "We are fighting human animals and are acting accordingly."

President Biden condemned Hamas's attacks, which have killed at least nine American citizens, calling it an "unprecedented and appalling assault." U.S. military ships have moved closer to the eastern Mediterranean in response to the recent escalation. Defense Secretary Lloyd Austin said on Sunday that he's "directed several steps to strengthen Department of Defense posture in the region to bolster regional deterrence efforts."

Recommended reading

The Associated Press: An Israeli airstrike kills 19 members of the same family in a southern Gaza refugee camp

Reuters:Ukraine's Zelensky calls for world solidarity with Israel

LA Times:Israel calls for complete siege of Gaza as it masses troops at border

Associated Press:These photos show fear, death and destruction in battle scenes from Israel and the Gaza Strip

Hamas

Hamas, or the Islamic Resistance Movement, is a militant organization that was created by a Palestinian cleric in 1987. The group does not consider Israel a legitimate state. Hamas has launched attacks against Israel over Israel's occupation of Palestinian territories Gaza and the West Bank. Since 2007, Hamas has led the de facto government of Gaza — an area densely populated by Palestinians near the Mediterranean Sea. The U.S. government and the European Union consider Hamas to be a terrorist organization.

Israel Defense Forces (IDF)

The Israel Defense Forces is the military branch of Israel that was established in 1948. Both men and women are expected to serve in the military for at least two years and remain in the reserves until their 50s.

Lion’s Den

Lion's Den is a Palestinian militant group that emerged from the West Bank in August 2022. The group's formation came in what was to be one of the worst years for Palestinians in the West Bank since 2005. Earlier this year, the New York Times labeled the group "small but influential."

Gaza Strip

The Gaza Strip is a 25-mile-long strip of land that has one of the highest population densities in the world. The strip, along with the West Bank, are the two Palestinian territories left of what used to be Palestine. The territory has been described by Human Rights Watch as the "world's largest open-air prison" as the shoreline and airspace as well as its land borders are all controlled by Israel.

Iron Dome

Israel’s Iron Dome aerial defense system blocks incoming rockets that have been launched from Palestinian territories.

Benjamin Netanyahu

Israeli Prime Minister Benjamin Netanyahu warned that Israel's response to the attacks would "change the Middle East" after he declared war on Hamas. Netanyahu leads a far-right ultra-conservative government that promotes Jewish settlements in Palestinian territories. In 2015, he said he would not allow a Palestinian state to be created — clearly going against the concept of a two-state solution. In September, Netanyahu presented a map to the United Nations General Assembly of the "New Middle East" where Palestine was not included.

But politically, Netanyahu has been at the center of an ongoing crisis where Israelis have taken to the streets to protest. In the first three months of this year alone, there had been hundreds of demonstrations in Israel over corruption.

Mohammed Deif

Mohammed Deif is the head of the military wing of Hamas and led "Operation Al-Aqsa Storm," the initial attacks on Israel that occurred on Saturday. Deif said the operation was in response to a 16-year-old blockade on Gaza as well as the recent incident at the Al-Aqsa Mosque in Jerusalem.

Ismail Haniyeh

Ismail Haniyeh is the leader of Hamas who resides in Qatar after fleeing Gaza several years ago. Ahead of Saturday's attack, he said: "In light of the continuing crimes against our people, in light of the orgy of occupation and its denial of international laws and resolutions, and in light of American and Western support, we've decided to put an end to all this … so that the enemy understands that he can no longer revel without being held to account."

Ali Khamenei

Ali Khamenei is the supreme leader of Iran who has been vocal about the country’s support of Hamas and its attack on Saturday. However, it has denied any involvement with the militant organization.

"The accusations linked to an Iranian role… are based on political reasons," a spokesman for Iran's foreign ministry said. Iran isn't involved in the "decision making of other countries." Israeli and U.S. officials remain unsure about Iran's involvement. "Just because you don't have that evidence doesn't necessarily mean Iran isn't behind it," Maj. Nir Dinar, a spokesperson for the Israel Defense Forces, told Politico.

Hezbollah

Hezbollah is a Lebanese militant group that has been operating since 1992. On Sunday, Hezbollah launched missiles at Israeli positions in the contested border area in what it said was “in solidarity” with Hamas. "We recommend Hezbollah not to come into this,” Richard Hecht, an Israeli army spokesman, said. “If they come, we are ready.”