September 1950, aircraft of the USAF's Far East Air Forces began attacks on roads and bridges to isolate Kunsan, typical of the kind of raids expected prior to an invasion there. A naval bombardment of Kunsan followed on 6 September, and on 11 September USAF B-29 Superfortress bombers joined the aerial campaign, bombing military installations in the area. In addition to aerial and naval bombardment, UN forces took other measures to focus North Korean attention on Kunsan. On the docks at Pusan, USMC officers briefed their men on an upcoming landing at Kunsan within earshot of many Koreans, and on the night of 12–13 September 1950 the Royal Navy frigate landed US Army special operations troops and Royal Marine Commandos on the docks at Kunsan, making sure that North Korean forces noticed their visit. UN forces conducted a series of drills, tests, and raids elsewhere on the coast of Korea, where conditions were similar to Incheon, before the actual invasion. These drills were used to perfect the timing and performance of the landing craft, but also were intended to confuse the North Koreans further as to the location of the invasion. Incheon infiltration Fourteen days before the landing at Incheon, a UN reconnaissance team (KLO Unit) landed in Incheon 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 Incheon to collect further intelligence on the area, was mounted by the US military. The tides at Incheon have an average range of and a maximum observed range of , making the tidal range there one of the largest in the world and the littoral maximum in all of Asia. Clark observed the tides at Incheon for two weeks and discovered that American tidal charts were inaccurate, but that Japanese charts were quite good. Clark's team provided detailed reports on KPA artillery positions and fortifications on the island of Wolmido, at Incheon and on nearby islands. During the extended periods of low tide, Clark's team located and removed some North Korean naval