Initially it consisted of only two infantry brigades which had been formed in Australia and dispatched to Britain in order to defend against a possible invasion following the Fall of France—the 18th and 25th Brigades—under the command of Major General Henry Wynter.

It was during this time that the division suffered its first casualties when German bombers attacked the transport column in which the 2/13th Battalion was travelling, killing two Australians and wounding one other.

As a result, the 9th Division commander, Leslie Morshead, ordered the 20th Brigade to withdraw from the frontier, moving 160 miles (260 km) back towards Benghazi.

[10] As the Axis advance continued with German victories at Marsa Brega and Agedabia which threatened to outflank the units cut off in Benghazi, the 9th Division were ordered to fall back from their positions along the coast to the east to Derna.

In order to achieve this, the 2/13th Battalion was used as a rear guard and late in the afternoon of 4 April it undertook the division's first action of the war when the Germans attacked their positions in the Er Regima Pass.

[13] Supported by British artillery, the battalion, spread out across an 11-kilometre (6.8 mi) front, managed to delay a German force of about 3,000 personnel mounted in lorries and accompanied by armoured cars and tanks.

[12] Two days after the action at Er Regima Pass, the 9th Division was ordered to fall back along the coast road towards Tobruk in what was later called the "Benghazi Handicap".

Due to the speed of the Axis advance and the division's lack of transport, confusion reigned and part of the 2/15th Battalion, including most of its headquarters and its commanding officer, were captured.

The following day, Tobruk was effectively placed under siege when German forces cut the supply road to its east, encircling the Allied garrison.

[14] This attack was beaten off, although that night a force of Germans with mortars and machine guns managed to break into the defences only to be counterattacked by a small group of Australians, including John Edmondson, armed with bayonets and grenades.

[18] The Australian defence of Tobruk was anchored on three factors: the use of the pre-existing Italian fortifications around the port, aggressive patrolling and raiding of Axis positions and the firepower of the garrison's artillery.

[19] After the failure of the British attempts to relieve the fortress in May and June 1941 the 9th Division was successful in gradually improving Tobruk's defences through aggressively raiding Axis positions.

[22] After its withdrawal from Tobruk the 9th Division enjoyed only a brief period of rest in Palestine before being redeployed to northern Syria where, as part of the British Ninth Army, it was responsible for guarding the Turkish–Syrian frontier.

It was decided that the British Eighth Army should make a stand just over 100 kilometres (62 mi) west of Alexandria, at the railway siding of El Alamein, where the coastal plain narrowed between the Mediterranean Sea and the inhospitable Qattara Depression.

[27] On 1 July, Rommel's forces made a major attack, hoping to dislodge the Allies from the area, take Alexandria, and open the way to Cairo and the Suez Canal.

On 6 July, the lead elements of the 9th Division arrived at Tel el Shammama 22 miles (35 km) from the front,[28] from where they would be committed to the fighting in the northern sector.

[29] Following the fighting in July, the 9th Division remained in front-line positions around El Alamein, but were engaged in mainly static defensive duties for the next three months.

[35] By late October 1942, the Eighth Army, now commanded by Lieutenant-General Bernard Montgomery, decided to launch its own offensive in the Western Desert, amassing a force of some 220,000 personnel supported by 1,100 tanks and 900 artillery pieces.

[36] The 9th Division was positioned in the northern sector of the Eighth Army's front at El Alamein, nearest the coast, as part of British XXX Corps.

While XIII and most of XXX Corps failed to meet their objectives on 25 October, the 9th Division gained considerable momentum, attacking both frontally and executing a wide "left hook" from their original positions, in their sector, with one Axis outpost after another falling to them.

[22] In October 1942 the Australian government requested that the 9th Division be released from service in the Middle East and returned to Australia to be utilised against the Japanese in the Pacific.

35 minutes later as the 26th Brigade came ashore, they were attacked by nine Japanese aircraft which inflicted a number of casualties on the Australians in the LCIs, with eight personnel being killed, including the commanding officer of the 2/23rd Battalion, while another 20 were wounded.

[57] Nevertheless, after a week of heavy fighting against well-entrenched Japanese troops, the Australians captured the town and airfield of Finschhafen, declaring it liberated on 2 October.

[62] Due to rapid developments in the war and strategic uncertainty over the role of Australian forces in the Pacific, the 9th Division remained in Australia for over a year before seeing action once more.

At 0656 hours the main assault began as the LCIs carrying the two battalions that would lead the attack—the 2/23rd and 2/48th—crossed the line of departure and headed towards the landing beach at Lingkas.

[73] Following a preliminary naval and aerial bombardment, the 24th Brigade landed at the southern end of Labuan island, which situated as it was at the entrance of Brunei Bay, commanded the approach to northern Borneo.

[75] The 24th Brigade, however, encountered greater opposition in taking the island of Labuan,[75] where the defenders withdrew to an inland stronghold where they held out along dense jungle covered ridges and muddy swamps.

[74] In order to subdue the Japanese resistance an intense naval and artillery bombardment was laid down over the course of a week before an assault was put in by two companies of infantry supported by tanks and flamethrowers.

[76][81] Following the end of the war the 9th Division remained in Borneo and performed emergency relief and occupation duties until the arrival of Indian troops in January 1946.

While the majority of the division's personnel returned civilian life after the war, some continued to serve with the British Commonwealth Occupation Force in Japan,[82] joining the 66th Infantry Battalion.