After the successful breakout from the Chinese encirclement in the Chosin area of North Korea with the 1st marine Division on 10-11 December 1950, B Company, 185 Engineer Combat Battalion was assigned a demolition mission by X Corps. It consisted of preparing the major railroad bridge south of Hamhung, a 2,100 foot- long structure consisting of 29 spans of single track deck girder bridging supported on concrete piers for destruction.

On 0700, 12 December 1950, the 3rd Platoon, commanded by 1st Lt. John E. Gately, moved to the site to commence work. Each span was about 75 feet long and the distance from the rails to the river bed about 30 feet, The river at that time was only 40-50 feet wide and three feet deep covered with a thin layer of ice. Seven or eight spans had been damaged previously by bombing. These sections had been repaired by using wooden rail cribbing built up to the level of the track or damaged girder. In some cases the rails were laid directly on the tie cribbing.