Under heavy international pressure, Israeli forces withdrew in March 1957, after heavily mapping the territory and placing secret supply caches in preparation for the next war. As part of the conditions for the Israeli withdrawal, the Sinai was demilitarized and the UNEF peacekeeping force was established there to police the border between Israel and Egypt. In May 1967, Egyptian President Gamal Abdel Nasser ordered the withdrawal of this force and moved Egypt's own troops into the area.