World War I

Bourchier commanded a CMF light horse troop at Numurkah, Victoria from 1909 to 1914. At the outbreak of World War I he was commissioned into the 4th Light Horse Regiment and left with the first contingent of the First Australian Imperial Force.^[2] He served with the regiment in the Gallipoli, Egyptian, Sinai, Palestine and Syrian campaigns.

While on Gallipoli he was appointed temporary captain on 1 July 1915 and adjutant of the 4th Light Horse Regiment on 7 September. He became the acting commander of "A" Squadron on 19 October 1915 and gained his substantive captaincy on 22 November. He was promoted to major on 20 January 1916. The recommendation for promotion noted that "he was always quite cool and collected, and this had a very good effect upon his men".^[3] He assumed full command of "A" Squadron on 1 February 1916.

Bourchier was promoted to lieutenant colonel on 15 March 1917 and took command of the 4th Light Horse Regiment. On 31 October 1917 he led the 4th and 12th Regiments in the four-mile charge against Turkish positions at the Battle of Beersheba, capturing 15 of the 17 wells intact and taking over 700 prisoners. In a later report he summed up the effect of the attack:^[4]

In commenting on the attack I consider that the success was due to the rapidity with which the movement was carried out. Owing to the volume of fire brought to bear from the enemy's position by Machine Guns and rifles, a dismounted attack would have resulted in a much greater number of casualties. It was noticed also that the morale of the enemy was greatly shaken through our troops galloping over his positions thereby causing his riflemen and machine gunners to lose all control of fire discipline. When the troops came within short range of the trenches the enemy seemed to direct almost all his fire at the horses.

He received the Distinguished Service Order on 4 November 1917:^[5]

For the gallant and capable manner in which as Commanding Officer of the 4th Australian Light Horse regiment he personally directed his Regiment into action on the attack on BEERSHEBA on 31 October 1917. This officer, by his skilful handling of his Regiment and by his magnificent example of courage and determination, was very largely instrumental in the success of the attack and capture of the town.

In September 1918 Bourchier again commanded a joint force of the 4th and 12th Regiments ("Bourchier's Force") in the final advance on Damascus, capturing 12,000 Turks. He was awarded the Companion of the Order of St Michael and St George on 3 June 1919 for the following recommendation:^[6]

In the face of a very heavy fire this officer led his regiment on 27 Sept. across the JORDAN below JISR BENAT YAKUB over a very difficult crossing and thus outflanked the enemy and compelled his to withdraw from the position. On 30 Sept. this officer was in command of the 4th and 12th A.L.H. [Light Horse] Regiments which formed the advanced guard of the [Australian Mounted] Division in its advance from SASA to DAMASCUS. He captured the enemy's position at KAUKAB by a spirited mounted charge of two Regiments without any delay and thus opened the way to DAMASCUS where his troops were the first to enter.

He took temporary command of 4th Light Horse Brigade in November–December 1918 while Brigadier William Grant was in temporary command of the ANZAC Mounted Division. During the war he was mentioned in dispatches three times.^[7] The regiment returned to Australia in June 1919.

Post war

After the war Bourchier returned to his farm near Strathmerton, Victoria. He remained an officer in the Australian Citizens Military Forces, becoming colonel in command of the 5th Cavalry Brigade in 1921 and Brigadier in command of the 2nd Cavalry Division in 1931.^[1]