Wooden stumps were installed in locations along the “Brisbane Line” to force tanks to rise up, exposing the belly for attack with explosives. The rugged terrain would have forced enemy vehicles to have to use roads, which would have been destroyed. Tank traps and boulders were part of the defensive line.
A brown sign is fixed to the cement wall opposite the tank traps with the following:
Tank traps which were erected during the war (these are to the left of the cement wall, in the form of posts standing upright). This is the area of the Brisbane Line which was to be the second line of defence if the northern part of Australia fell into enemy hands. During the war up to 10,000 troops were camped in the Tenterfield district.
A walking track connects the WW2 tank traps with Thunderbolt’s Hideout 
, located about 1km towards Tenterfield.
The Brisbane Line was a line drawn from Brisbane to Adelaide, although some maps show it as Brisbane to Perth. The theory behind it was that Australia was unable to protect its huge coastline should an invasion occur. By concentrating troops along this line, it would offer better protection to the more densely populated areas to the south, and people living north of the line would be evacuated.
Many of the tank traps around Australia were positioned in locations where the terrain would force motorised military vehicles to negotiate existing roads. The tank traps established at Thunderbolt’s Gully were for this reason. The huge boulders on the Eastern hillside were considered too much of an obstacle for light tanks. The concrete retaining wall running parallel to the road was built to prevent any military vehicle bypassing the road, which would have been rigged with explosives in the case of an invasion.
Three rows of heavy wooden posts were erected to force enemy tanks to rise up, allowing defending troops to fire an explosive charge at their exposed soft underbelly. The rock fall further down from the posts was from rock blasted up higher to make the passage more difficult. Drill holes can still be seen in this fallen rock.
During the Pacific Campaign, up to 10,000 troops were stationed in and around Tenterfield. One of the major training camps, London Bridge, was located 3 kilometres south of the Tank Trap site.
There are also concrete pyramid Tank Traps at Paddy’s Flat, further to the east, which were another integral part of Australia’s defenses during the War.
Fortunately, The Battle of the Coral Sea saw the turning point of the war which prevented the feared invasion of Australia.
