Official Historian Gavin Long described him as "perhaps the clearest and most profound thinker the Australian Army of his generation had produced.

Wynter's public criticism of the government's Singapore strategy led to his being reduced in rank and sent to Queensland.

Wynter embarked for the Middle East in May 1940 with the advance party of I Corps but the convoy he was travelling with was diverted to the United Kingdom.

[2] Wynter joined the First Australian Imperial Force on 24 April 1916 as a major, having been promoted to the brevet rank on 1 December 1915.

[3] Wynter embarked for the United Kingdom from Sydney with the 11th Infantry Brigade headquarters on the transport HMAT Demosthenes on 18 May 1916,[5] arriving on 20 July 1916.

On 24 March 1917, he was transferred to I Anzac Corps headquarters as its Deputy Assistant Adjutant General (DAAG).

On 6 July 1918 he was among a small number of Australian officers who accompanied General Sir William Birdwood to Fifth Army headquarters.

[2] Wynter published a paper on the command of the Imperial forces in wartime in the British Army Quarterly in 1925.

[2] Following the visit of the British Cabinet Secretary, Sir Maurice Hankey, to Australia in 1934, political interest in the Singapore Strategy debate rose.

[4] On 5 November 1936, the Leader of the Opposition, John Curtin used the paper to bolster a strong attack on the policies of the Minister for Defence, Archdale Parkhill.

In retaliation, in March 1937, Parkhill had Wynter posted to the staff of the 11th Mixed Brigade in Queensland at his substantive rank of lieutenant colonel, with a consequentially reduced salary.

[4] In April 1940, I Corps was formed and Wynter accepted an offer from Lieutenant General Sir Thomas Blamey to become its Deputy Adjutant and Quartermaster General, its senior administrative officer, "a post somewhat smaller than his exceptional experience and talents deserved but the highest the overseas force could offer in the field".

[3] Wynter embarked from Melbourne on 15 May 1940 with the advance party of I Corps with orders to establish a base organisation in the Middle East but the convoy he was travelling with was diverted to the United Kingdom.

[17] Up until a couple of days before it arrived, the convoy had been under the command of Brigadier Leslie Morshead of the 18th Infantry Brigade but on 18 April, Wynter discovered that the Military Board back in Australia had promoted him to major general and appointed him to command the AIF in the United Kingdom.

Wynter decided that, given the immediate danger of a German invasion of the United Kingdom, his force had to be ready to fight.

[21] In Blamey's reorganisation of the Army in April 1942, Wynter was appointed Lieutenant General Administration (LGA) at Allied Land Headquarters in Melbourne.