The Landing at Nadzab was an airborne landing on 5 September 1943 during the New Guinea campaign of World War II in conjunction with the Landing at Lae. The Nadzab action began with a parachute drop at Lae Nadzab Airport, combined with an overland force. The development of Nadzab was delayed by the need to upgrade the Markham Valley Road. After strenuous efforts in the face of wet weather, the road was opened on 15 December. Nadzab then became the major Allied air base in New Guinea.