On the recommendation of Brigadier General Robert Anderson, the Commandant,
Administrative Headquarters, AIF, and against the opposition of Birdwood, Senator Pearce appointed McCay as commander of the AIF Depots in the United Kingdom.
These depots received and trained reinforcements arriving from Australia, and rehabilitated and retrained convalescents who were released from hospital.
McCay established his headquarters at Tidworth, in the heart of the Salisbury Plain where most of the Australian camps were located.
He occupied this post for the remainder of the war, failing in bids to return to an active command at the head of the 5th Division, the Australian Corps, or the 3rd Division when Monash was promoted to corps commander.
A bid to replace Birdwood as administrative commander of the AIF also came to naught.
For his services in the United Kingdom, McCay was mentioned in despatches a fourth time, made a Knight Commander of the Order of St Michael and St George in 1918, and a Knight Commander of the Order of the British Empire in 1919.

On 10 March 1919, McCay handed over command of the AIF Depots in the United Kingdom to Major General Charles Rosenthal.
After a farewell dinner hosted by Monash, he embarked for Australia, where his AIF appointment was terminated.
In 1919, along with George Swinburne and Generals White and Legge, he produced a report on the organisation of the post-war Army.
In 1920, he joined Generals Chauvel, White, Monash, Legge, and Hobbs to produce a second report on the subject.
McCay retired from the Army in 1926 with the honorary rank of lieutenant general.
On the recommendation of Brigadier General Robert Anderson, the Commandant,
Administrative Headquarters, AIF, and against the opposition of Birdwood, Senator Pearce appointed McCay as commander of the AIF Depots in the United Kingdom. These depots received and trained reinforcements arriving from Australia, and rehabilitated and retrained convalescents who were released from hospital. McCay established his headquarters at Tidworth, in the heart of the Salisbury Plain where most of the Australian camps were located. He occupied this post for the remainder of the war, failing in bids to return to an active command at the head of the 5th Division, the Australian Corps, or the 3rd Division when Monash was promoted to corps commander. A bid to replace Birdwood as administrative commander of the AIF also came to naught. For his services in the United Kingdom, McCay was mentioned in despatches a fourth time, made a Knight Commander of the Order of St Michael and St George in 1918, and a Knight Commander of the Order of the British Empire in 1919.
On 10 March 1919, McCay handed over command of the AIF Depots in the United Kingdom to Major General Charles Rosenthal. After a farewell dinner hosted by Monash, he embarked for Australia, where his AIF appointment was terminated. In 1919, along with George Swinburne and Generals White and Legge, he produced a report on the organisation of the post-war Army. In 1920, he joined Generals Chauvel, White, Monash, Legge, and Hobbs to produce a second report on the subject. McCay retired from the Army in 1926 with the honorary rank of lieutenant general.
James Whiteside McCay