Engineer’s Daily Duties
Field fortification of positions and acting as infantry reserves were part of the engineer’s daily duties. During defensive battles, engineer units mined the forward terrain at night and repaired damaged minefields. During the day, they manufactured improvised mines and traps.
The movement of enemy tanks was restricted by building obstacles and cutting trenches into ice-covered lakes and rivers. The blocking value of the Saimaa Canal was maintained by regulating water flow.
Demolition work was used to inflict casualties on advancing enemy forces. The timely detonation of the Koirinoja bridge and the 2.5-kilometer stretch of road in Lemetti caused the enemy to suffer up to 700 casualties and the loss of several tanks.
Engineers destroyed enemy tanks that breached the positions using satchel charges and incendiary bottles. At best, an engineer company destroyed 10–15 tanks in a single day of combat.
In the motti battles northeast of Lake Ladoga, engineers fought alongside the infantry as riflemen, opened supply routes, blocked enemy withdrawal from encirclements with mines and barricades, and destroyed enemy strongholds and entrenched tanks.
Further north, engineers built bypass trails through roadless terrain and mined road cut-off points. In the Salla and Petsamo areas, in addition to other engineer tasks, snow plowing was emphasized across a total road network of 3,500 kilometers.
The satchel charge and Molotov Cocktail were invented in the Engineer Battalion (Pioneeripataljoona) before the war.
Snow plowing. Time and place unknown.
Fortification Work
Construction troops under the Engineers Commander of the General Headquarters built reinforced concrete fortifications. Over 600 construction engineers and supervisors held managerial positions on the work sites. In March 1940, there were 17,000 workers. Troops and construction units of the formations dug trenches and communication lines, built gun emplacements, obstacles, and dugouts. In many places, work started before the war continued.
Training Activities
Reinforcement personnel assigned to the front received rapid combat training at the Engineer Training Center in Koria. Key subjects in the branch-specific training included mining and booby-trapping. Training also covered the use of close-range anti-tank weapons. The training center also housed the engineer line of the Reserve Officer School and a non-commissioned officer school. The 800 bombs dropped during Soviet air force attacks aimed at destroying the bridges in Koria failed in their objective but destroyed a residential building in the barracks area and gave trainees a foretaste of war.