In 1966, Black and white TV broadcasts began. On 15 May 1967, the first public performance of Naomi Shemer's classic song "Jerusalem of Gold" took place and over the next few weeks it dominated the Israeli airwaves. Two days later Syria, Egypt and Jordan amassed troops along the Israeli borders, and Egypt closed the Straits of Tiran to Israeli shipping. Nasser demanded that the UNEF leave Sinai, threatening escalation to a full war. Egyptian radio broadcasts talked of a coming genocide. On 26 May Nasser declared, "The battle will be a general one and our basic objective will be to destroy Israel". Israel considered the Straits of Tiran closure a Casus belli. Egypt, Syria, Jordan and Iraq signed defence pacts and Iraqi troops began deploying to Jordan, Syria and Egypt. Algeria also announced that it would send troops to Egypt. Between 1963 and 1967 Egyptian troops had tested chemical weapons on Yemenite civilians as part of an Egyptian intervention in support of rebels.