The first spaced armors were used on iron (then steel) warships from mid 19th century. Between the thin outer armor of various less important parts and the thick main armor (protecting turrets, ammunition depots, boilers and turbines) were constructed storage spaces, coal or oil bunkers, and so on (Lord Nelson class). Some ships (e.g. Tirpitz, Takao, King George) had thicker outer and thinner inner layers in order to lower the damage caused by the penetrating round. From 1900 some cruisers and battleships were built with modern spaced armor, where the outer thin layer was intended only to damage the projectiles (e.g. Littorio class).