The term "battle cruiser" for the period 1905-1920. can be defined as the designation of a ship at least four knots faster than a contemporary battleship, armed with guns suitable for the main caliber artillery of contemporary battleships, and with such armor protection as is possible if the two previous conditions are met. The difficulties in creating a satisfactory design for such a ship, the displacement of which might be less than that of the corresponding battleships, or, with a few exceptions, would not be much more than theirs, consisted in the large size and weight of the boilers, machinery and mechanisms necessary to provide higher speed. Battlecruisers were probably, as they were conceived in England, suitable both for regular cruising service and for use in battle as a fast division of the main force. The second task immediately received preference over the others.