Egypt is threatening to void its decades-old peace treaty with Israel. What does that mean?

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 a decades-old peace treaty.

It was a warm handshake between the unlikeliest of statesmen, conducted under the beaming gaze of then-U.S. 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.

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.