The United States has pledged unequivocal support for ally Israel, underlining its right to defend itself after an unprecedented incursion by Hamas militants from the Gaza Strip killed at least 1,300 people there and wounded about 3,300.

President Biden denounced the attacks by Hamas, a militant group that controls the Gaza Strip and has been designated a terrorist organization by the United States since 1997, as “sheer evil,” in a speech on Tuesday. “We stand with Israel. And we will make sure Israel has what it needs to take care of its citizens, defend itself, and respond to this attack,” he said.

Biden’s forceful remarks — and promise of military aid — underscore the close, historical relationship between Israel and the United States.

The United States was the first country to recognize Israel when it declared independence in 1948. Israel is the largest recipient of U.S. foreign aid; Washington provides $3.3 billion annually in military aid and an additional $500 million in missile defense funding. The United States has provided Israel a total of $158 billion, according to the Congressional Research Service.

Here’s what to know about U.S. and Israel relations, and what Washington has said so far about Israel’s war with Gaza.

What is the U.S. doing as the Israel-Gaza war begins?

Amid fears this could turn into a wider regional conflict, this week U.S. Central Command dispatched a carrier strike group to the eastern Mediterranean sea as a step to deter other actors from joining the conflict. The USS Gerald R. Ford aircraft carrier was sent “to deter any actor seeking to escalate the situation or widen this war,” the military said in a statement. A senior defense official previously told The Washington Post that the United States is “deeply concerned” about the possibility that Hezbollah — the Iranian-backed Shiite militant group and political party that is Lebanon’s most dominant armed force — will join the conflict. Analysts also say there’s a risk tensions will escalate further if Israel and Washington blame Iran, which has helped arm and train Hamas, for the attack.

The Biden administration is also maintaining close contact with the Israeli government as 17 Americans remain unaccounted for — at least some of whom are believed to have been taken captive by Hamas. At least 25 Americans were killed in the attack, Secretary of State Antony Blinken said as he arrived in Israel on Thursday in a show of support and solidarity.

U.S. government officials have been deployed to consult and advise the Israeli government on hostage recovery, Biden said in his White House remarks Tuesday. “I have no higher priority than the safety of Americans being held hostage around the world,” he said.

Blinken was also in Israel to work on the emerging hostage crisis. As he boarded a plane at Joint Base Andrews, Blinken told reporters that the United States wants “to make sure to the best of our ability — and I know Israel wants to make sure to the best of its ability — that civilians are not harmed” in Gaza. Israeli forces have bombed the densely-populated strip — which has been under a joint Egyptian-Israeli blockade since 2007 — have cut off Gazans’ access to water and fuel in a retaliatory “siege” for the Hamas attack on Israel and are massing troops near the enclave. Washington has not condemned the siege, which U.N. human rights commissioner Volker Türk on Tuesday said was “prohibited under international humanitarian law.”

“Israel has to take steps to defend itself,” Blinken said Thursday. “It has to make sure that any ongoing threat is dealt with - and I believe it has to make sure that, going forward, what happened doesn’t happen again.” What military aid is the U.S. sending to Israel?

The first plane carrying American ammunition landed Tuesday at Israel’s Nevatim Air Force Base. Cooperation between the armies of the two countries is a “key part of ensuring regional security,” Israel Defense Forces spokesperson Daniel Hagari said. The Department of Defense has ordered more advanced fighter jets including F-16s to squadrons in the region, it said this week. Officials are also working to expedite shipments of military equipment already ordered by Israel. National Security Council spokesman John Kirby told reporters this week that the United States had “no intention to put U.S. boots on the ground.”

Central Command in its statement said the forces in the area include the U.S. Navy aircraft carrier USS Gerald R. Ford, with its eight squadrons of attack and support aircraft, along with a Ticonderoga class guided missile cruiser and guided missile destroyers.

In his remarks on Tuesday, Biden said he would ask Congress to approve an urgent military aid package for Israel. But that task has been complicated by the recent ouster of Rep. Kevin McCarthy (R-Calif.) as House speaker, which has left the chamber in limbo.

In the aftermath of the attack, Israeli officials have requested that Washington replenish Israel’s stockpile of Iron Dome ground-to-air missile interceptors, small-diameter bombs and ammunition for machine guns, The Washington Post has reported. Israel has requested more cooperation on intelligence-sharing, particularly in southern Lebanon, U.S. officials told The Post.

Washington sends aid to the Palestinian territories each year for humanitarian purposes and to support the western-backed Palestinian Authority based in the West Bank. Trump cut more than $200 million in funding to Palestinians in 2018, but the aid was restored and expanded under the Biden administration. Between April 2021 and March 2022, the United States provided slightly more than $500 million in humanitarian aid to Palestinians through organizations such as the United Nations and the U.S. Agency for International Development, the State Department said. Biden last year announced an additional $316 million in aid that included funding for hospitals and improved internet connectivity in the Palestinian territories. What is the Biden administration’s position on the Israeli-Palestinian conflict?

The Biden administration has echoed a long-standing U.S. position that the best outcome is “a comprehensive, negotiated two-state solution.” But there have been no meaningful peace negotiations in years, and experts and analysts say the growing number of Israeli settlements in the West Bank, as well as instances of violence between settlers and Palestinians, has made the prospect of a two-state solution increasingly remote.

In July 2022, a few months into his term, Biden traveled to the West Bank and met with Palestinian Authority President Mahmoud Abbas. Biden said he still supports the creation of independent Israeli and Palestinian states, formed within borders approximately equivalent to what existed before the 1967 war. Israel defeated Egypt, Jordan, and Syria, capturing the Sinai Peninsula, the Golan Heights, Gaza, the West Bank and East Jerusalem.

The Biden administration has also lobbied regional power-broker Saudi Arabia to establish closer trade, security and political ties with Israel, and the State Department has said that it is “dedicated to deepening and expanding normalization and integration between Israel and Arab and Muslim-majority states.” This built on the Trump administration’s efforts to achieve normalization between Israel and its neighbors. Under Trump, Israel signed normalization agreements with Bahrain, the United Arab Emirates, Sudan and Morocco. What is Biden and Netanyahu’s relationship?

Biden and Netanyahu have both held positions of political leadership in their respective countries for decades and have a long personal history of cooperation as well as disagreement. Biden has been pointed in his criticism of settlement expansion and violence in the West Bank under Israel’s current far-right government. Most recently, the two traded public barbs over Netanyahu’s refusal to call off his proposal to limit the Supreme Court’s power in Israel, with Biden saying in March that he was “very concerned” and telling reporters, “they cannot continue down this road.”

Biden waited months to invite Netanyahu to the White House after he began his sixth term — a move that was widely perceived in Israel as a slight.

According to the State Department’s records, Netanyahu in his years as prime minister has traveled to the United States 27 times for official visits, working trips and to attend international summits or sign treaties.

But the two leaders appeared to patch over some of their differences and in September, when Biden and Netanyahu met in New York on the sidelines of the U.N. General Assembly, Biden invited him to the White House for an official visit before the year’s end. Before the meeting, Biden said, “even where we have some differences, my commitment to Israel, you know, is ironclad.” Tyler Pager, Liz Sly, Ishaan Tharoor, Abigail Hauslohner, Amy B Wang, Steve Hendrix, Toluse Olorunnipa and Meryl Kornfield contributed to this report.