About one week prior to the Inchon invasion, a joint CIA-military operation "Trudy Jackson" sent in a tough guerilla unit led by Navy Lt. Eugene Clark, an Old China hand ex-CPO. His team included an Army captain, three EMs and two Korean military specialists, and landed on Yonghung-do, a small island at the mouth of the channel, ten miles from Inchon. Helped by the small civilian population, Clark's men scouted the tides, mud-flats and seawalls, getting vital last minute information for the assault. They were completely successful in this, even reconnoitering fortified Wolmi-do!
The NK soon found the guerillas were there, and sent an assault craft with 16 infantrymen to attack them, but Clark met them in the channel with a .50 machine gun on a sampan, and sank them all. In a major accomplishment, Clark got an old light-house working on Palmi-do, which provided a critical navigation point for our Naval forces.
The down side, when Clark moved his small unit to Palmi-do, the NK came back unopposed to Yonghung-do, lined up 50 South Koreans who had helped Clark, and murdered them. A favorite NK tactic. (My major personal regrets about the KW are that we never rounded up the guys who did tens of thousands of murders like those, and hanged them all. )
Bert Kortegaard, Inchon veteran