JERUSALEM (AP) — It was a warm handshake between the unlikeliest of statesmen, conducted under the beaming gaze of President Jimmy Carter. Sunlight streamed through the trees at Camp David, Maryland, as Egyptian President Anwar Sadat and Israeli Prime Minister Menachem Begin solidified a landmark agreement that has allowed over 40 years of peace between Israel and Egypt. It has served as an important source of stability in a volatile region.

That peace has held through two Palestinian uprisings and a series of wars between Israel and Hamas. But now, with Prime Minister Benjamin Netanyahu vowing to send Israeli troops into Rafah, a city in Gaza on the border with Egypt, the Egyptian government is threatening to void the agreement.

Here’s a look at the history of the treaty and what could happen if it is nullified.

HOW DID THE TREATY ORIGINATE?

It was 1977, and Begin, Israel’s new prime minister, opposed ceding any of the land Israel had conquered a decade earlier in the 1967 Mideast war. Those lands included Egypt’s Sinai Peninsula.

Egypt and Israel had fought four major wars, most recently in 1973. So it shocked the world when Egypt’s Sadat broke with other Arab leaders and decided to engage with the Israelis.

The talks culminated in the Camp David Accords in September 1978 and a peace treaty the following year.

Under the peace treaty, Israel agreed to withdraw from the Sinai, which Egypt would leave demilitarized. Israeli ships were granted passage through the Suez Canal, a key trade route. The countries established full diplomatic relations in Israel’s first peace agreement with an Arab country.

“The Camp David Accords were led by three brave men who took a bold stance because they knew the lasting effects for peace and security, both then and for the future. We need the same kind of leadership today, and that is currently lacking,” said Paige Alexander, chief executive of the Carter Center.

WHAT IS EGYPT’S CURRENT POSITION?

Two Egyptian officials and a Western diplomat told The Associated Press on Sunday that Egypt may suspend the peace treaty if Israeli troops invade Rafah.

Netanyahu says Rafah is Hamas’ last remaining stronghold after more than four months of war and that sending in ground troops is essential to defeat the group.

But Egypt opposes any move that could send desperate Palestinians fleeing across the border onto its territory. Rafah also serves as the besieged territory’s main entry point for humanitarian aid, and an Israeli attack could stifle the deliveries of key supplies.

Rafah’s population has swelled from 280,000 people to an estimated 1.4 million as Palestinians flee fighting elsewhere in Gaza. Hundreds of thousands of those evacuees are living in sprawling tent camps.

Netanyahu has ordered the military to prepare a plan to evacuate all Palestinian civilians before the offensive starts. But it is unclear where they will go.

Netanyahu said Sunday that they would be able to return to open spaces farther north. But those areas have been badly damaged by the Israeli offensive.

WHAT HAPPENS IF THE TREATY IS VOIDED?

The treaty greatly limits the number of troops on both sides of the border. This has allowed Israel to focus its military on other threats.

Along with the war in Gaza, Israel has engaged in near-daily skirmishes with the Hezbollah militant group in Lebanon while its security forces deploy heavily in the occupied West Bank.

If Egypt were to nullify the agreement, it could mean that Israel can no longer rely on its southern border as an oasis of calm. Bolstering forces along its border with Egypt would no doubt challenge an Israeli military already thinly stretched.

But it would bear serious ramifications for Egypt as well. Egypt has received billions of dollars in U.S. military assistance from the U.S. since the peace agreement.

If the agreement is voided, it could jeopardize that funding. A massive military buildup would also strain Egypt’s already struggling economy.

Alexander said any step that could draw Egypt into the hostilities “would be catastrophic for the entire region.”

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