Warship A warship is a ship that is built and primarily intended for combat . As well as being armed , warships are designed to withstand damage and are usually faster and more maneuverable than merchant ships . Unlike a merchant ship , which carries cargo , a warship typically only carries weapons , ammunition and supplies for its crew . Warships usually belong to a navy , though they have also been operated by individuals or companies . In wartime , the distinction between warships and merchant ships is often blurred . In war , merchant ships are often armed and used as auxiliary warships , such as the Q - ship s of the First World War and the armed merchant cruisers of the Second World War . Until the 17th century it was common for merchant ships to be pressed into naval service and not unusual for more than half a fleet to be composed of merchant ships . Until the threat of piracy subsided in the 19th century , it was normal practice to arm larger merchant ships such as galleon s . Warships have also often been used as troop carriers or supply ships , such as by the French Navy in the 18th century or the Japanese Navy during the Second World War . Evolution of warships . The age of galleys . In the time of Mesopotamia , Ancient Persia , Ancient Greece and the Roman Empire , the most common type of warship was the galley ( such as bireme s , trireme s and quinquereme s ) , a long , narrow vessel powered by banks of oar smen and designed to ram and sink enemy vessels , or come alongside the enemy so its occupants could be attacked hand - to - hand . However with the development of catapults in the 4th century BC and the subsequent refinement of its technology enabled the first fleets of artillery equipped warships by the Hellenistic age . With the political unification of the Mediterranean Sea in the 2nd and 1st centuries BC , naval artillery fell out of use . Throughout late antiquity and the Middle Ages until the 16th century , naval warfare relied on the ship itself , used as a ram , the swords of the crew , and various missiles such as bows and arrows and bolts from heavy crossbow s fixed on a ship ' s bulwark s . Naval warfare primarily involved ramming and boarding actions , so warships did not need to be particularly specialized . The age of sail . Naval artillery was redeveloped in the 14th century , but cannon did not become common at sea until the guns were capable of being reloaded quickly enough to be reused in the same battle . The size of a ship required to carry a large number of cannons made oar - based propulsion impossible , and warships came to rely primarily on sails . The sailing man - of - war emerged during the 16th century . By the middle of the 17th century , warships were carrying increasing numbers of cannon on their broadside s and tactics evolved to bring each ship ' s firepower to bear in a line of battle . The man - of - war now evolved into the ship of the line . In the 18th century , the frigate and sloop - of - war – too small to stand in the line of battle – evolved to convoy trade , scout for enemy ships and blockade enemy coasts . Steel , steam and shellfire . During the 19th century a revolution took place in the means of propulsion , armament and construction of warships . Steam engines were introduced , at first as an auxiliary force , in the second quarter of the 19th century . The Crimean War gave a great stimulus to the development of guns . The introduction of explosive shells soon led to the introduction of iron , and later steel , armour for the sides and decks of larger warships . The first ironclad warships , the French " Gloire " and British " Warrior " , made wooden vessels obsolete . Metal soon entirely replaced wood as the main material for warship construction . From the 1850s , the sailing ships of the line were replaced by steam - powered battleship s , while the sailing frigate s were replaced by steam - powered cruiser s . The armament of warships also changed with the invention of the rotating barbette s and turret s , which allowed the guns to be aimed independently of the direction of the ship and allowed a smaller number of larger guns to be carried . The final innovation during the 19th century was the development of the torpedo and development of the torpedo boat . Small , fast torpedo boats seemed to offer an alternative to building expensive fleets of battleships . The Dreadnought era . Another revolution in warship design began shortly after the start of the 20th century , when Britain launched the all - big - gun battleship " Dreadnought " in 1906 . Powered by steam turbines , she was bigger , faster and more heavily gunned than all existing battleships , which she immediately rendered obsolete . She was rapidly followed by similar ships in other countries . Britain also developed the first battlecruiser s . Mounting the same heavy guns as the Dreadnoughts on an even larger hull , battlecruisers sacrificed armour protection for speed . Battlecruisers were faster and more powerful than all existing cruisers , which they made obsolete , but battlecruisers proved to be much more vulnerable than contemporary battleships . The torpedo - boat destroyer was developed at the same time as the Dreadnoughts . Bigger , faster and more heavily gunned than the torpedo boat , the destroyer evolved to protect the capital ship s from the menace of the torpedo boat . Second World War . During the lead - up to the Second World War , Germany and Great Britain once again emerged as the two dominant Atlantic sea powers . Germany , under the Treaty of Versailles , had its navy limited to only a few minor surface ships . But the clever use of deceptive terminology , such as " panzerschiffes " deceived the British and French commands . They were rudely surprised when ships such as the " Admiral Graf Spee " , " Scharnhorst " , and " Gneisenau " constantly raided the Allied supply lines . The greatest threat though , was the introduction of the Kriegsmarine ' s most lethal weapons , the " Bismarck " and " Tirpitz " . The Bismarck was sunk in a wild , short series of sea battles in the north Atlantic , while the Tirpitz caused a bit of a stir before being knocked out by the Royal Air Force . The British Royal Navy gained dominance of the European theatre by 1943 . The Second World War brought massive changes in the design and role of several types of warships . For the first time , the aircraft carrier became the clear choice to serve as the main capital ship within a naval task force . World War II was the only war in history in which battles occurred between groups of carriers . World War II saw the first use of radar in combat . It brought the first naval battle in which the ships of both sides never engaged in direct combat , instead sending aircraft to make the attacks , in the Battle of Coral Sea . Development of the submarine . The first practical submarine s were developed in the late 19th century , but it was only after the development of the torpedo that submarines became truly dangerous ( and hence useful ) . By the end of the First World War submarines had proved their potential . During the Second World War the German Navy ' s submarine fleet of U - boat s almost starved Britain into submission and inflicted huge losses on US coastal shipping . The success of submarines led to the development of new anti - submarine convoy escorts during the First and Second World Wars , such as the destroyer escort . Confusingly , many of these new types adopted the names of the smaller warships from the age of sail , such as corvette , sloop and frigate . Development of the aircraft carrier . A major shift in naval warfare occurred with the introduction of the aircraft carrier . First at Taranto and then at Pearl Harbor , the aircraft carrier demonstrated its ability to strike decisively at enemy ships out of sight and range of surface vessels . By the end of the Second World War , the carrier had become the dominant warship . Modern warships . Modern warships are generally divided into seven main categories , which are : aircraft carrier s , cruiser s , destroyer s , frigate s , corvette s , submarine s and amphibious assault ship s . Battleships encompass an eighth category , but are not in current service with any navy in the world . Only the deactivated American Iowa - class battleship s still exist as potential combatants , and battleships in general are unlikely to re - emerge as a ship class without redefinition . The destroyer is generally regarded as the dominant surface - combat vessel of most modern blue water navies . However , the once distinct roles and appearances of cruiser s , destroyer s , frigate s , and corvette s have blurred . Most vessels have come to be armed with a mix of anti - surface , anti - submarine and anti - aircraft weapons . Class designations no longer reliably indicate a displacement hierarchy , and the size of all vessel types has grown beyond the definitions used earlier in the 20th century . Another key differentiation between older and modern vessels is that all modern warships are " soft " , without the thick armor and bulging anti - torpedo protection of World War II and older designs . Most navies also include many types of support and auxiliary vessels , such as minesweeper s , patrol boat s and offshore patrol vessels .