1914-1918 1939-1945 1961-1975 20thcentury armedforces australian belgium campaigns designandconstruction discoveriesingeography discoveryandexploration engineeringandconstruction flanders fortification france history military militarycampaigns militaryengineering militaryparticipation militaryweapons participation treasuretroves tunneling tunnels vietnam vietnamwar weaponssystems westernfront worldwar worldwar(1914-1918)