On 10 December 1944 orders were given to construct a High Level Bailey Bridge across the River Lamone to replace the 200-foot demolished bridge (M.4273, 65) on Via Cortina, the road leading to Bagna Cavallo (M.3938). This bridge was originally required to assist 1 Canadian Infantry Brigade in retaining the bridgehead across the river. The bridge site was very exposed and under enemy observation from Bagna Cavallo and possibly Traversara (M.4337). Initial attempts at reconnaissance of the bridge site drew considerable enemy small arms, mortar and artillery fire. During the morning of 11 December, No.2 Platoon, 13 Canadian Field Company started work on the bank seats but by 1000 hours, when the ground mist lifted, the site became untenable for the rest of the morning due to intermittent enemy fire.
At 1400 hours the same day, No.3 Platoon, 13 Canadian Field Company, Royal Canadian Engineers took over the task. Sergeant Armstrong was in charge of erection parties. Intermittent fire continued throughout the afternoon but did not interfere with the construction of the bridge until 1830 hours when a very heavy concentration of Nebelwerfers rained down on the site. Sergeant Armstrong shouted a warning to the men to take cover but remained on the bridge himself to ensure that the remainder took cover quickly. Two bombs hit the bridge, several hit the approach roads and the remainder fell in the area of the slit trenches.
Immediately the firing ceased, the Sergeant assisted his officer in rallying the men back to work and arrived back on the bridge just in time to give warning of the follow-up repeat performance. The task under the direction of this Non-Commissioned Officer was finally completed at 1000 hours the following morning.
Throughout the entire bridging operation Sergeant Armstrong's actions were an inspiration to all. His watchfulness and warning to the men in case of danger, his complete disregard of his own personal safety and his qualities of leadership enabled the operation to proceed with all possible speed toward a successful conclusion.