Towards the end of the war, movement returned to the western front. The NZ tunnellers found that their jobs at the front now included road repair and bridge construction. They are credited with construction of the biggest bridge ever erected during the First World War, a feat for men many of whom had never constructed bridges before.
During September 1918, about 70 NZ Tunnellers practised bridge construction at Rosel in Normandy. General Little, Chief Engineer of the Third British Army, and General Harvey, Chief Engineer of the fourth Corps, seemed very interested in these men during a visit to Rosel camp. Their interest in the New Zealanders urged them to choose this unit for the erection of the Havrincourt bridge over the Canal du Nord.
Begun in 1913, this canal was still under construction at the outbreak of the war. The Canal formed a kind of huge trench without water. In September 1918, it defined a front between the British and Germans Armies. A British offensive under preparation by the end of September 1918. If the attack was to succeed, a bridge would have to be built to carry supply vehicles and also to allow for the passage of reinforcements.
The construction site of the bridge was not easy. The site was the crossing of the Canal du Nord by the Hermies - Havrincourt road. At this point passing through a cutting 100 ft deep and with a distance of 180 ft between the tops of the smooth brick walled sides of the canal. Bridges designed by the British Army covered 120 ft maximum, not enough to link the two side of the Canal. The NZ Tunnellers would join two bridges together to form only one large construction. From an engineering point of view the task verged on the impossible.
On the morning on 27th September 1918, the First and Third British Armies attacked the German front line located near the Canal du Nord. The offensive was the starting signal for the NZ Tunnellers bridge building to begin.
In order to optimize the performance, the whole force was divided into two shifts. The first worked from dawn to midday and the second took over from then till dark. At 6am, the Tunnellers began work on the skeleton of the bridge. The plan envisaged the erection of the bridge on the west side while on the east side, two wooden towers were constructed to pull and to carry the bridge over the canal.
The bridge structure was placed on slides which would guide the bridge over the canal. In four days, the structure was ready for the great manoeuvre. A counterweight of 20 tons built with rail and placed at the end of the bridge. Winches were installed on the two towers, which could lift a total weight of 70 tons.
By 5pm on 1st October the launching operation began. Three days later, the structure was slowly slipping away from the other side of the canal. But the weight of the bridge tilted the frame slightly so that it was 12 ft (3,65m) below the level of the bank. The two wooden towers had only served to pull the bridge over the canal, not to lift it.
The supreme part of the manoeuvre started. Any failure at this time would have spelt disaster. Both winches operated and slowly lifted the iron structure. Inch by inch, the frame was closer to the level of the bank. About 6pm, the bridge was lifted several inches above the ground level of the bank. The bridge was slowly pulled for the last time and linked both sides of the Canal. It was an amazing feat for men who never erected bridge under the conditions of which they were operating.
Between the end of September 1918 and the Armistice day, the New Zealand Tunnellers followed the infantry men in their advance. The front line was not paralysed any more. In seven weeks, the front knew the most important and major retreat of the war. The allied armies were in route from the North Sea until the Meuse imposing a general fold of the enemy towards the East.
The men initially crossed the old battlefields, a landscape completely devastated by four years of keen fights. Then, they arrived for the first time on unknown lands. The maps could only helped the armies to go forward on a country strewn with channels and rivers. Moreover, the German obvious positions did not help the British soldiers in their advance and attacks.
The Allied advanced carefully. The enemy was increasingly weak. Nonetheless, the crossed territories are parcelled out. The work of the Royal Engineers was great. The main communication ways were cut off and they must be quickly repaired: roads, railways and bridges. The engineers were full of works. The Tunnelling companies provided a welcome help.
The New Zealanders worked on bridges construction for reinforcing the advanced troops. The Tunnellers were not on the first line and they were employed a few miles behind the front in movement from Cambrai to Maubeuge. Their bridges were very important to go forward.