A U.S. nuclear-powered submarine collided with a Japanese oil tanker at the entrance to the Persian Gulf this week, causing light damage to the tanker but no injuries. The tanker was able to pull into a nearby United Arab Emirates port for repairs. The bump from behind took place as the two were passing through the Strait of Hormuz between Iran and Oman, the conduit for 40 percent of the worlds oil. It wasnt the first such accident. A fleet of U.S. vessels patrols the Persian Gulf area to prevent smuggling of weapons to Iraq and Somalia and of nuclear components to Iran. In 2005, a U.S. aircraft carrier ran over a small sailboat, killing the occupants.