 The Indefatigable class were the second class built of British battlecruisers which served in the Royal Navy and the Royal Australian Navy during World War I. The design represented a modest reworking of the preceding Invincible class , featuring increased endurance and an improved cross @-@ deck arc of fire for their midships wing turrets achieved by a lengthening of the hull . Like its predecessor , the design resembled the contemporary dreadnought of the Royal Navy , but sacrificed armour protection and one turret from the main battery for a 4 @-@ knot ( 7 @.@ 4 km / h ; 4 @.@ 6 mph ) speed advantage . 
