Ever since it occupied the Sinai in 1967, Israel had openly declared it would remain in Sharm el-Sheikh to ensure the sea lanes to the port of Eilat through the Straits of Tiran remained opened (the closing of the Straits to Israeli shipping in 1967 was one of the causes of the Six-Day War). Egypt aimed to nullify Sharm el-Sheikh's importance to Israel by imposing a naval blockade at the straits of Bab-el-Mandeb, almost from Israel. To this end, arrangements were made with Pakistan to receive Egyptian vessels for repair early in 1973. Approval was sought, and obtained, from Sudan and Yemen to receive the submarines on their way to Pakistan in Port Sudan and Aden as a friendly visit. Pakistan's approval to receive Egyptian vessels for repairs were made public. On 1 October, a force containing several submarines, destroyers and missile boats set sail on a route planned to ensure their arrival at Bab-el-Mandeb on October 6. The fleet was fully equipped for combat, and the force was ordered to maintain complete radio silence; which meant there was no way of recalling the submarines. The commanding officers, unaware of their real mission, were issued sealed envelopes detailing their orders and mission, and were instructed to open the envelopes on 6 October, only a few hours before the war was to begin, whereupon they would break their radio silence. Once the fleet had set sail that day, 1 October, ""the war had effectively begun"".