[4] On 26 August 1914, the RCHA mobilized the Royal Canadian Horse Artillery Brigade, CEF and on 30 September 1914, the regiment embarked for Great Britain.
[4] On 1 September 1939, the Royal Canadian Horse Artillery was mobilized for active service as the 1st Field Brigade, RCA, CASF.
In June 1940, the regiment arrived in France as part of the Second British Expeditionary Force, reaching a point west of Le Mans before being ordered back to the UK.
The regiment landed in Sicily in July 1943 and in Italy in September 1943, providing field artillery support for the 1st Canadian Infantry Division.
[4] On 1 June 1945, a second Active Force component of the regiment was mobilized for service in the Pacific theatre of operations under the designation of the 1st Canadian Field Artillery Battalion, RCA, CASF.