As a soldier, McCay commanded the 2nd Infantry Brigade in the landing at Anzac Cove on 25 April 1915, during the Gallipoli Campaign of the Great War.

After the war, McCay resumed his old job as Deputy Chairman of the State Bank of Victoria and also served on a panel that deliberated on the future structure of the Army.

He completed his law degree the next year, with first class honours, in spite of rarely attending the lectures due to his work, political and military commitments.

[13] When the prominent local Member of the Legislative Assembly, Sir James Patterson, died in 1894, McCay ran for his seat of Castlemaine in the resulting by-election.

McCay, who characterised himself as a liberal, supported the widest possible enfranchisement of women, the protection of industry and revenue through tariffs, and the White Australia policy.

The war in South Africa was now in its final stages and the electorate forgot or forgave McCay's "treason", electing him to the first Australian Parliament.

[19] As a backbencher, McCay opposed amendments to the Defence Act 1903 proposed by Billy Hughes of the Australian Labor Party that called for peacetime conscription.

In 1910, the Commonwealth Liberal Party Senate candidate, Thomas Skene, died suddenly two days before the nomination date for the 1910 election.

[32] In 1911, McCay delivered a lecture at the Victorian United Services Institution entitled "The True Principles of Australia's Defence".

Soon after the outbreak of the Great War on 4 August, Bridges, now a brigadier general, appointed McCay to command the 2nd Infantry Brigade of the Australian Imperial Force (AIF).

The exception was his youngest appointment, Lieutenant Colonel Harold Elliott of the 7th Infantry Battalion, a University of Melbourne educated lawyer like himself.

[37] On 21 October McCay and his brigade headquarters embarked from Melbourne on the former P&O ocean liner RMS Orvieto, which also carried Major General Bridges and the staff of his 1st Division.

[45] The commander of the Mediterranean Expeditionary Force, General Sir Ian Hamilton, now decided to make his main effort at Cape Helles.

[46] The Australian and New Zealand Army Corps commander, Lieutenant General Sir William Birdwood, was ordered to send a brigade from each of his two divisions to Helles to reinforce the British and French troops there.

[47] On the evening of 8 May, during the Second Battle of Krithia, McCay was given 35 minutes notice to conduct an advance across open ground in broad daylight.

[52] McCay, Monash and Colonel Harry Chauvel were all disappointed at being passed over for the command, and protested to Birdwood and the Australian government, but to no avail.

[54] He arrived back in Melbourne on RMS Malwa on 11 November 1915,[55] accompanied by his two teenage daughters and his brother Hugh, who had joined the ship in Adelaide, to a hero's welcome.

[56] For his service at Gallipoli, McCay was mentioned in despatches[57] for his "great promptitude in supporting the threatened flank of the covering force" during the landing and his "conspicuous gallantry" at Krithia.

Owing to a shortage of rolling stock, the 4th and 5th Divisions were ordered to undertake a three-day route march across the desert under service conditions, carrying their packs and weapons.

He made tactical errors: his failure to pass on Haking's cancellation orders led to the annihilation of the now-unsupported 58th's men before crossing the field, described by C.E.W.

Bean as one of the bravest and most hopeless assaults ever undertaken by the Australian Imperial Force; his order to vacate the first trench after it was cleared "undoubtedly contributed to the causes of failure".

[75] Nonetheless, McCay remained in command of the 5th Division until 18 December 1916 when he was granted medical leave in the United Kingdom for treatment on his leg, which the doctors diagnosed as neuralgia.

[1] McCay resumed his old job as Deputy Chairman of the State Savings Bank of Victoria on 10 June 1919, a few days after he returned to Melbourne.

On 30 December 1919, the Premier of Victoria, Harry Lawson, McCay's successor in Legislative Assembly seat of Castlemaine and a former student at Castlemaine Grammar and Scotch College, appointed McCay as chairman of the Fair Profits Commission, a consumer protection body set up to monitor prices and profits.

McCay ran this organisation from the Melbourne Town Hall, and later the Repatriation Department offices, which were made available rent free by the Commonwealth Government.

[85] McCay's daughter Mardi matriculated from Sacré Cœur School in 1914 and earned Master of Arts and Diploma of Education degrees from the University of Melbourne.

Bixie also attended Sacré Cœur and the University of Melbourne, at Janet Clarke Hall, where she became only the third woman in Victoria to earn a Master of Laws degree, and was enrolled as a barrister on 10 June 1925.

[4] He was given, at his request, a non-military funeral at Cairns Memorial Presbyterian Church in East Melbourne, and was buried at Box Hill Cemetery.

General Sir Brudenell White considered McCay to be "one of the greatest soldiers that ever served Australia, greater even than Monash.

[91] A revival of interest in Australian military history and the rediscovery of graves at Fromelles in the 21st Century led to a number of books being written about the battle, which tended to be critical of McCay.