In mid-1942, the strategic situation in the Pacific was desperate for the Allies with the Fall of Singapore in February 1942 and the Japanese victory in the Dutch East Indies campaign.

Its first commander was Major General Edmund Herring, who arrived at a time when an invasion was expected and comprehensive changes to tactical dispositions were delayed.

[1] As the threat passed, at the end of April, Herring reorganised his force extending the fortress area to include RAAF Base Darwin and strengthening its defences.

The 2/4th Independent Company was assigned patrolling duties around Katherine and the 2/6th Cavalry Regiment occupied Pine Creek.

In July 1943, defence plans were revised and the area that the garrison was expected to cover was concentrated around Darwin rather than its hinterland.

The 12th Brigade continued defensive duties around Darwin until the end of the war in August 1945, when it was finally deployed as part of Timor Force.

[7] Following this, the size of the force was slowly reduced as part of the demobilisation process and the majority of its units were supply, transport, maintenance, medical, signals and engineer units spread across Darwin, Alice Springs and Mount Isa, although there was a small artillery element based around Darwin's fixed defences.