15 September was chosen because the high tides would be at their maximum. Unfortunately, the morning high tide came at 06:59; only 45-minutes after sunrise and the second high tide was at 19:19 hours; 37-minutes after sunset. Neither of these times was ideal, and the next opportunity wasn’t till October. That’s primarily why it was a 2-phase operation.

I’ve read somewhere (?) that a small contingent of pathfinders/UDT went quietly ashore on the two harbor islands and even checked out Inchon itself for obstacles such as mines, gun emplacements etc. Unfortunately, I don’t have info on that pre-invasion incursion.

A good book on the subject is: “Victory at High” Tide by Robert Heinl. Published by Lippencott in 1968.

On the morning of 15 September 1950 the 3rd Battalion, 5th Marines supported by tanks, air and naval gunfire landed and seized the two harbor islands of Wolmi-do and Sowolmi-do. According to my sources NO Marines were killed during the assault on these islands.

Due to the erratic tidal conditions it wasn’t until late in the afternoon of the 15th that the 1st and 5th Marine Regiments hit the beaches at Inchon.

This operation was probably the only sensible one which came out of “Dugout” Doug’s brain. Most of the other military geniuses believed Inchon was too far North and wanted to go ashore 100-miles South, but Doug held out for Inchon and the rest is history.