 Steam @-@ powered screw frigates were built in the mid @-@ 1840s , and at the end of the decade the French Navy introduced steam power to its line of battle . The desire for change came from the ambition of Napoleon III to gain greater influence in Europe , which required a challenge to the British at sea . The first purpose @-@ built steam battleship was the 90 @-@ gun Napoléon in 1850 . Napoléon was armed as a conventional ship @-@ of @-@ the @-@ line , but her steam engines could give her a speed of 12 knots ( 22 km / h ) , regardless of the wind conditions : a potentially decisive advantage in a naval engagement . 
