Lieutenant General Robert Harold Nimmo, CBE (22 November 1893 – 4 January 1966) was a senior Australian Army officer who served in World War I, in World War II, with the British Commonwealth Occupation Force in Japan, as general officer commanding (GOC) Northern Command in Australia, and finally as the chief military observer of the United Nations Military Observer Group in India and Pakistan from 1950 until his death in 1966.

Soon after the Japanese surrender, Nimmo was selected to command the 34th Brigade, and led it from Morotai in the Dutch East Indies to Japan, where it formed part of the British Commonwealth Occupation Force.

[2] Nimmo was appointed as a lieutenant in the Permanent Military Forces upon graduation on 3 November 1914,[3] having held the position of the senior cadet of his 40-strong class, known as the company sergeant major.

On 21 December the regiment sailed from Sydney for the Middle East aboard SS Persic, a White Star Line ocean liner that had been converted into a troopship and redesignated HMAT A34.

[5] On 4 February 1916 Nimmo reported to the Australian personnel depot in the UK after recuperating from his illness, and a month later he departed to return to the Middle East, sailing on the SS Arcadian, another converted liner used as a troopship.

[3] In March 1916 the 5th Light Horse Regiment had joined the ANZAC Mounted Division forming in Egypt, and was involved in the defence of the Suez Canal from an Ottoman advance, although its main task was long-range patrolling.

[11] By this time, the 5th Light Horse Regiment was based at Dueidar – west of Katia on the northern Sinai Peninsula, from where extensive patrolling and reconnaissance was conducted.

[11] Nimmo led B Squadron during several minor brigade and regimental operations targeting enemy patrols and outposts in the vicinity of Beersheba in July,[22] and August,[23] before spending September engaged in training and inspections at the rest camp at Tel el Marakeb.

[25] Nimmo led his squadron during the successful Battle of Beersheba on 31 October,[5] where the 5th Light Horse Regiment helped cut the Beersheba-Hebron road at Sakati to isolate the Ottoman defenders.

[26] The presence of the 2nd Light Horse Brigade across the Beersheba-Hebron road helped to give the German general commanding the Ottoman forces in the sector, Friedrich Freiherr Kress von Kressenstein, the false impression that the Allied advance would now be aimed at Jerusalem, and he made troop dispositions that weakened the defences at Gaza.

[27] Nimmo's squadron then participated in the follow-up operations around Tel el Khuweilfe in the first few days of November, which were initially led by the 5th Light Horse Regiment.

[28] Soon after, the 5th Light Horse Regiment participated in the successful Third Battle of Gaza on 7 November, where it advanced quickly with exposed flanks to attempt to cut off the retreating Ottoman forces at Huj, but was unable to reach its objective despite fighting "dashingly".

[30] In late November and early December, the 5th Light Horse Regiment held a defensive position along the Auja river, before the entire brigade received a week's rest.

[34] On 26 March, two squadrons of the 5th Light Horse Regiment – one of which was Nimmo's[35] – attacked a convoy on the Amman-Es Salt road, and captured two dozen vehicles and 12 prisoners,[36] and on the following day cut the railway to the north of Amman by blowing up a bridge.

[49] Upon his return to Australia, Nimmo was presented the 1915 Sword of Honour,[50] an award for the cadet in each Duntroon graduating class who displays the most exemplary conduct and performance of duties.

This was followed by a posting in July of the same year as assistant adjutant & quartermaster general (AA&QMG) of the 2nd Cavalry Division, headquartered in Melbourne, which included formations based in Victoria and South Australia.

On 16 March 1937, Nimmo embarked for the UK to attend the 54th course of the British Army's Senior Officers' School at Sheerness in Kent between 27 September 1937 and 15 December 1937, and returned to Melbourne on 6 June 1938.

[58] According to his entry in the Australian Dictionary of Biography, Nimmo calmly handled the so-called "Morotai incident" in January after his brigade was subjected to delays and public criticism which had nearly resulted in mutiny, impressing many.

[65] In early 1950, in the wake of the Indo-Pakistani War of 1947–1948, the Australian diplomat and jurist Sir Owen Dixon was appointed as the United Nations (UN) mediator between India and Pakistan over the disputed State of Jammu and Kashmir.

Unable to get the Prime Minister of India, Jawaharlal Nehru, to agree to take the steps necessary to ensure that the plebiscite would be fair and free, Dixon's report criticised both sides for not reaching an agreement.

[68] The role of UNMOGIP was to monitor the 800-kilometre (500 mi) long ceasefire line between the Indian and Pakistani armed forces, which began in the lowland Kashmir Valley and extended through rugged and mountainous territory to the Himalayas in the north.

His Australian chief of staff initially performed his duties in his absence, but eventually the Belgian Major General Bennett Louis de Ridder was appointed as acting CMO for three months.

The UN Secretariat suggested that Nimmo be promoted to lieutenant general to overcome this issue, and in recognition of his "outstanding ability, both in military matters and in diplomatic functions which he has been called on to perform".

Defence pointed out that Nimmo was on the Retired List and could not be substantively promoted, but that he could be granted the honorary rank of lieutenant general while he remained with UNMOGIP.

[2][73] In the same year, Indian complaints about the American observers resulted in the end of their contribution to UNMOGIP, and according to the Australian High Commissioner to India, Walter Crocker, Nimmo was content to see them go, as he did not consider them suited to the role.

[76] In 1964, the UN Secretariat reported that Nimmo was "by far the most successful United Nations observer ever",[60] and the official war historians assert that "his professional expertise and diplomatic skills" ensured UNMOGIP was well run, despite its inability to solve the Kashmir problem.

[78] According to the official historians, Nimmo's actions and correspondence during the war indicate that he had "thought deeply about ways of easing the conflict in Kashmir and was trying to impose realistic solutions".

[80] According to the historian Peter Londey, Nimmo had an extraordinary understanding of his role, which he fulfilled "through maintaining an open, firm but tactful relationship with both the belligerent parties, and [showing] favour to neither".

[2] After an Anglican service in Rawalpindi with Pakistani military honours and fellow Australian observers as pall bearers, his body was flown to Karachi and then Brisbane.

[2] His obituary in The Morning Bulletin newspaper in Rockhampton, Queensland, stated that he performed his duties "impeccably" and had "added considerably to Australia's stature internationally".