PREPAREDNESS, AS any Boy Scout knows, is important. Even the ancient Canaanites knew it, as evidenced by the recently discovered 26 foot high walls built with 4-5 ton boulders in Jerusalem. The walls connected to towers with walls 12-and-a-half feet thick, all to guard the path to the city’s only water supply, the Gihon Spring. So who or what was such a threat in 1800 B.C. that you needed 26-foot walls to keep them out?