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

Egyptian President Anwar Sadat, left, U.S. President Jimmy Carter, center, and Israeli Prime Minister Menachem Begin clasp hands on the North lawn of the White House as they completed signing of the peace treaty between Egypt and Israel in Washington on March, 26, 1979. Egypt has threatened to void its decades-long peace treaty with Israel if Israel begins a large-scale offensive on Rafah, where some 1.4 million Palestinians shelter in densely-packed tent camps on the border with Egypt. (Bob Daugherty/AP-File)