Fourteen days before the landing at Inchon, a UN reconnaissance team landed in Inchon Harbor to obtain information on the conditions there. The team, led by US Navy Lieutenant Eugene F. Clark, landed at Yonghung-do, an island in the mouth of the harbor. From there, the team relayed intelligence back to the UN Command. With the help of locals, Clark, gathered information about tides, beach composition, mudflats, and seawalls. A separate reconnaissance mission codenamed "Trudy Jackson", which dispatched Lieutenant Youn Joung of the Republic of Korea Navy and ROK Colonel Ke In-Ju to Inchon to collect further intelligence on the area, was mounted by the US military.