While the loading of X Corps ran its course, other developments in the objective area threatened even more directly than supply and shipping problems to wreck the entire landing operation. The enemy had mined Wonsan Harbor and all its approaches.
The U. S. Navy had discovered enemy mines in Korean waters as early as 4 September. Operations at Inch'ŏn had been somewhat hampered by contact mines laid in the entrance channel. (Magnetic mines had also been discovered but, fortunately, ashore.)