The operation on the edge of the Strait of Hormuz employs a shuttling technique long used by Iran to skirt sanctions. DUBAI, June 16 (Reuters) - The United States military has overseen scores of secretive ship-to-ship oil transfers to keep Gulf energy exports flowing, using aerial and water drones as well as helicopters in an operation to guide convoys to awaiting tankers. The operation on the edge of the Strait of Hormuz employs a shuttling technique long used by Iran to skirt sanctions. Two