Her propulsion system consisted of two 3-cylinder triple-expansion steam engines powered by eight coal-fired, cylindrical fire-tube Scotch marine boilers.

[2] The ship was armed with a main battery of four BL 12-inch (305 mm) Mk VIII guns in twin-gun turrets, one forward and one aft.

She was also equipped with five 18 in (457 mm) torpedo tubes, four of which were submerged in the ship's hull, with the last in a deck-mounted launcher.

This allowed Mars and her sisters to have a deeper and lighter belt than previous battleships without any loss in protection.

[1] The barbettes for the main battery were protected with 14 in (356 mm) of armour, and the conning tower had the same thickness of steel on the sides.

She was present at the Fleet Review at Spithead for the Diamond Jubilee of Queen Victoria on 26 June 1897.

With war appearing to be imminent, the Royal Navy undertook a precautionary mobilization on 27 July 1914.

As part of this, Mars and her sister ships Hannibal, Magnificent, and Victorious formed the 9th Battle Squadron, which was based in the Humber under the Admiral of Patrols.

Mars and her similarly disarmed sister ships Hannibal and Magnificent, also acting as troopships, arrived at Mudros on 5 October 1915.

At the Dardanelles, Mars took part in the evacuation of Allied troops from Anzac Cove on 8 and 9 December 1915 and from West Beach at Cape Helles on 8 and 9 January 1916.

During the West Beach evacuation, Mars was covered by what had once been her 12-inch (305-mm) guns, now mounted on Sir Thomas Picton.

Mars returned to Devonport in February 1916, then paid off at Chatham, where she underwent a refit for conversion to a harbor depot ship.