The official beginning of the Royal Canadian Navy came with the passage of the Naval Service Act in May, 1910. In order to institute this new branch of the fighting services it was necessary to recruit and train both officers and men, and until such time as Canadian seamen could be considered sufficiently efficient, men would have to be borrowed or transferred from the Royal Navy. To provide the ships in which to train the expected influx of recruits an armored cruiser, Niobe, and a lighter cruiser, Rainbow, were purchased from the Admiralty[1].
The Apollo’s were already obsolete by the time the two were offered to Canada as training ships at the 1909 Imperial Defense Conference. By 1908 twelve ships including Rainbow had been listed as available for subsidiary purposes. Some of these were in the process of being, or had already been converted to minelayers.[2] Nevertheless Canada agreed in 1910 to purchase Rainbow as a training ship and for fishery protection duties for £50,000. Rainbow arrived in Canada in 1910 with a gun armament largely similar to that which she was originally commissioned in 1892[3].
With the election of the Borden government September 1911, the new navy entered what Commander Walter Hose later termed its “Heart breaking starvation time”[4], and the Rainbow engaged in very little activity. However, with the outbreak of the First World War on August 4th 1914, the Rainbow was brought back to some semblance of operational readiness. With her tasking quickly changed to patrol duties on declaration of war[5], she immediately recommenced gunnery practice, conducting a full battle test on the first day of the war by firing twelve rounds of 6-inch, thirty-one of 4.7-inch and sixteen of 12-pounder ammunition at 4000 to 2000 yards.[6] This firing, however, was conducted using practice ammunition – the only type she had on board at the time. It would not be until after Rainbows initial sorties in searches for the German cruiser Leipzig ranging as far south as San Francisco that she would finally receive her arsenal of proper Lyddite filled shells.[7]
After the situation in the Pacific stabilized and the threat from Germanys West Asiatic Squadron was eliminated by Sturdee’s battle cruisers at the Falkland Islands in December 1914, Rainbow continued her Pacific patrols in support of trade protection and sea control. By 1917, however, with the U-boat attacks on trade threatening to push Britain out of the war, the Rainbows guns and crew were urgently needed in the Atlantic, and in May 1917, Rainbow was paid off. Her crews were sent to the East Coast to join the struggle, preceded by some of her guns. No further records covering further reductions to Rainbows remaining two 4.7-inch guns and the 12-pounders have come to light, but it is likely that they too went to counter the U-boat threat in the Atlantic[8]. The 6-inch guns, however, stayed with the ship[9].