In 1940–1942, the corps was based in the Mediterranean and Middle Eastern theatres, and controlled forces in action against the Germans, Italians and later the Vichy French in North Africa, Greece and Syria–Lebanon.

Forces assigned to the corps undertook garrison duties in Ceylon, and briefly deployed to the ill-fated defence of Java in 1942, before returning to Australia.

[6] At this time, the main elements of the corps headquarters moved forward towards the combat zone, leaving the administrative staff in Gaza and establishing themselves in Ikingi Maryut, in Egypt.

On 12 April, it was officially renamed the Anzac Corps, a reference to the combined Australian-New Zealand formations of World War I.

However, on 18 June, prior to that objective being reached, I Corps headquarters – based at Nazareth – took charge, to improve command and control of the Allied forces.

[14] From this date all Allied troops in the theatre came under the command of Lieutenant General John Lavarack, who took over from Blamey when he became deputy commander-in-chief in the Middle East.

[15] Following the armistice in July, I Corps headquarters was established at Aley, near Beirut,[16] and assumed responsibility for occupying all of Lebanon and Syria north of the Beirut–Damascus road.

[19] The 9th Division would remain in the Middle East, though, upon request,[20] and would see further action in the First and Second Battles of El Alamein, where they would be assigned to the British XXX Corps.

[21] As the situation in the Pacific grew desperate for the Allies, plans were made to deploy I Corps headquarters, and the 6th and 7th Divisions, to Sumatra, Java,[19] or possibly to Burma to help stem the tide of the Japanese advance on Rangoon.

The Australian government ultimately rejected the request to divert the 7th Division to Rangoon,[22] and although most of the force returned to Australia, Lavarack was not able to prevent some elements from landing in Java – mainly the troops on the transport Orcades consisting of a machine gun battalion (the 2/3rd) and a pioneer battalion (the 2/2nd), as well as engineers, transport and medical personnel, who became part of Blackforce under Brigadier Arthur Blackburn.

[28] While the 16th and 17th Brigades were in Ceylon, the Army in Australia had undergone a significant reorganisation to meet the threat of a possible Japanese invasion.

[36] Meanwhile, in Australia, I Corps headquarters was re-established at Barrine, Queensland, where it took command of units resting and training prior to their commitment for further operations.

[37] In line with this, the 7th Infantry Division was transferred to I Corps at this time as they returned from New Guinea for rest, although they were based further south than the other elements, around Strathpine.

[35] In all locations, the objectives were captured, albeit against stronger-than-expected resistance in some cases, with commensurately heavy casualties, after which the Australians pushed further inland, carrying out mopping up operations.

On Tarakan, the airfield was captured five days after the landing, but it was badly damaged and ultimately filled no role in subsequent operations.

Meanwhile, in North Borneo, after operations to secure Labuan and Brunei had proved successful, a follow-up landing was made around Weston, with a subsequent advance towards Beaufort, which was captured after heavy engagement resulted in over 100 Japanese killed.

By mid-July, the main resistance around Balkipapan and the coastal areas had been overcome, and the defending Japanese had withdrawn into the hills further inland.

[43] Following the cessation of hostilities in August, the corps assumed responsibility for facilitating the Japanese surrender on Borneo and in making preparations for returning the area to Dutch colonial control in the post war period.

[35] This included undertaking local and protective patrols to maintain law and order and to secure Japanese soldiers who had not yet surrendered.