as part of the special operations group, or sog, udts successfully conducted demolition raids on railroad tunnels and bridges along the korean coast. on 15 september 1950, udts supported operation chromite, the amphibious landing at incheon. udt 1 and 3 provided personnel who went in ahead of the landing craft, scouting mud flats, marking low points in the channel, clearing fouled propellers, and searching for mines. four udt personnel acted as wave-guides for the marine landing.