As the United States continues to intensify its war against Iran, the transit of oil through the Strait of Hormuz is still choked off – and the ramifications are being felt around the world. CBS News national security correspondent David Martin talks with Retired General Frank McKenzie about the hazards facing American ships; and how long it might take the U.S. Navy to open the Strait, a vital shipping channel through which one-fifth of the world's oil flows.