"Defence" was ordered as part of the 1904–05 naval construction programme as the last of three armoured cruisers. She was laid down on 22 February 1905 at the Royal Dockyard in Pembroke Dock, Wales. She was christened on 27 April 1907 by Lady Cawdor and commissioned on 3 February 1909 at the cost of £1,362,970. The ship was briefly assigned to the 5th Cruiser Squadron of the Home Fleet until she was transferred to the 2nd Cruiser Squadron when the Home Fleet reorganised on 23 March 1909. Three months later "Defence" was reassigned to the 1st Cruiser Squadron. She escorted the ocean liner in 1911–1912 while the latter ship served as the royal yacht for the newly crowned King George V's trip to India to attend the Delhi Durbar. After the ship returned to Plymouth in early 1912, "Defence" was transferred to the China Station, where she remained until December when she was ordered to rejoin the 1st Cruiser Squadron in the Mediterranean as flagship.