The only road connecting the Dead Sea area with the rest of the country was the road to Jerusalem. Vehicles had been under attack on the road since the beginning of 1948 and travel was restricted to armed convoys. The road was finally completely cut off on April 10, 1948. From April 10 onwards the only contact with the Dead Sea area was by air. On May 20, 1948 all of the members of Kibbutz Beit Ha'arava, the Potash Company workers and the Hagana and Palmach contingents from the northern part were evacuated by sea to Sodom at the southern end. At the beginning, letters were carried from Sodom by the pilots, and entered the civilian or army postal systems, with or without stamps; an allocation of Army Post "KBA 192" to the Dead Sea area was made in June 1948. The earliest letter with a KBA 192 cachet was sent to Tel Aviv arriving 7 July 1948. Following the capture of Beer Sheba by the IDF, at the end of October 1948, preparation for opening the land route to Sodom began. The operational order to free Sodom was given on 20 November and Sodom was liberated on 25 November by soldiers of the Negev Brigade. This ended the siege.