The 104th Battery was mobilized in Fredericton, York County, New Brunswick on 15 July 1940 with Major W. F. Blair as O.C. Other officers included, Capt. E.D. Hall, Lieut. Y. McLean, Lieut. T.K. Stephens, Lieut. D.A. Wolstenholme, and Lieut. R.M. McGibbon. The new recruits received basic training at the experimental farm, located near Fredericton, following which they were shipped to Nickel Building, in Kingston, Ontario, and then on to Petawawa at the end of November 1940. At this time, the 104th Battery came under the command of the 4th Anti-Tank Regiment Royal Canadian Artillery.

In March 1941, the 104th Battery was moved to St. Stephen, New Brunswick. The following month, it embarked at Halifax, Nova Scotia, aboard the H.M.T. "Georgic", as an independent battery, destined for Gourock, Scotland. In Scotland the recruits received more anti-tank training. The 104th Anti-Tank Battery became a component of the 7th Anti-Tank Regiment RCA that was formed in England on 25 July 1941 to serve as 1st Canadian Corps Anti-Tank Regiment.

The 104th Battery boarded the "Scythia," on 12 November 1943, at Bristol, England, bound for the Mediterranean on operation "Timberwolf II". By 25 November 1943, the 104th had disembarked at Algiers, Algeria, North Africa. It later moved on to Sicily, France, and Holland. The Battery served in Holland under First Canadian Army until World War II ended. It disbanded in June 1945.