An American Arleigh Burke-class Aegis destroyer : 

A warship is a ship used by any country’s armed forces that have a Navy. They range from aircraft carriers to very small patrol boats. 

A warship is a weapon that had never disappeared from history, although its form had changed from the time when humans first started building ships to the present day. 

In this issue, we will learn about the history, basic structure, and various weapons and defense systems of warships.

“History of warships”

Ancient warships were not much different from civilian ships. The only difference was whether there were soldiers on board or not. 

As shipbuilding technology developed and naval warfare technology became more sophisticated, warships used only by the military appeared. The ancient Greeks, for example, built warships with many oars and wind sails. 

A boat with many oars needed a lot of rowers, so they needed a lot of food and water. So it was not very useful as a civilian ship because it could not carry a lot of cargo.  However, ships using oars could move with agility regardless of the wind direction, so most warships at that time had multiple oars. 

Before the invention of gunpowder, most naval fights required connecting a friendly ship close to the enemy ship, then having warriors with weapons climb aboard the ship and engage in hand-to-hand fighting. 

The other option was to use the horn mounted on the bow to destroy the enemy ship. Battleships that could launch several tons of shells up to 20 kilometers distance first appeared during World War II as the cannons grew larger and more potent.

After World War II, missiles became the primary weapon of battleships, while guns were treated as auxiliary weapons, being used seldom or never at all.

“The structure of the warship”

1. Type of engine

The size and weaponry of each nation’s big warships vary significantly, but overall, their construction is the same.

Engine example of a warship combining two diesel engines (center square) and two gas turbine engines (cylindrical on the right)

Inside the metal, the hull is a diesel, gas turbine, or a combination of the two engines. Diesel engines are similar to automobile diesel engines in fundamental principles, but as they are used on warships, they are powerful and large. 

A gas turbine engine is similar to the jet engine of an aircraft, but whereas the jet engine of an aircraft produces propulsion by a reaction by ejecting a strong jet backward, a gas turbine for a ship uses the jet to turn a type of high-speed windmill called a turbine, where it spins with a propeller in the water. While doing so, it gains the power to turn the wings (also called ‘screws’) that propel the ship.

A diesel engine is heavy compared to engine output but has good fuel efficiency, and a gas turbine engine is light and powerful compared to the engine output, but fuel efficiency is poor. 

So, depending on the mission, the warship is outfitted with either a diesel or a gas turbine engine, and both are designed to complement one another.

Some supercarriers and submarines use nuclear turbines. The device boils water with nuclear power and then turns a turbine with a large amount of steam generated. Once installed, a nuclear reactor can be used semi-permanently until the ship is disposed of and has tremendous power. 

The size of the ship itself must be substantial, and radiation hazards must be considered to accommodate a nuclear reactor and radiation shielding facilities.

2. Combat System

All ships have several windows outside, and a bridge is located in a high place so you can see the surroundings well. 

In general, all ships necessary for navigation are implemented on the bridge, but only basic navigation-related facilities are equipped on the bridge for warships. 

Exposing the bridge makes it vulnerable to enemy attacks Unless it is a small high-speed craft with little space inside, there is a separate space called the Combat Information Center (CIC) in the center of the warship.

Inside view of the battle command center (CIC) of the Aegis ship

 Here, the surrounding conditions captured by various sensors, friendly warships, and aircraft are linked to inform combatants with multiple texts and figures.

Combat personnel assess the environment following their missions, determine whether the opponent is nearby or posing a threat to me, and, if required, fire weapons.

The problem is that in wartime, many warships, aircraft, and enemy forces roam the area where battles occur in a situation where the success or failure of an operation goes back and forth in units of one second.

 It is unreasonable to judge all situations by the strength of the combatants alone. That’s why a computer connected to the battle system in a warship synthesizes various information and classifies and informs the combatants of the most threatening enemy.

 It even reduces the workload of combat personnel by automatically firing defense missiles and operating defense systems depending on the operating mode.

Various equipment of Arleigh Burke-class destroyers. From top left (excluding duplicate equipment description) Phalanx close-air anti-aircraft gun,

3. Radar and sensors

Modern warships generally use three types of sensors: radarsonar, and infrared sensors to understand their surroundings. Radar is a sensor that observes the surroundings using radio waves.

Daring-class destroyer with high radar to detect even beyond the horizon

A warship is equipped with radars that typically locate an enemy warship at sea, and an anti-air search radar, which simultaneously monitors a wide area of the sky to look for enemy aircraft and radar. It has an anti-aircraft tracking radar that accurately measures data like height and speed

When the size of a warship is too small to have a variety of radars, it is possible to put all of the various functions mentioned above into one radar and use it in different modes as needed.

Sonar is a sensor that keeps an eye on the ocean since radio waves have trouble traveling across it. Since sound waves can be transferred effectively even underwater, the sonar can identify the type, location, and speed of objects in the water by listening for the sound of enemy submarines or torpedoes by emitting sound waves when necessary.

An infrared sensor is a device that monitors the surroundings using a kind of infrared camera and helps detect small ships, low-flying enemy aircraft, or missiles.

When radar employs radio waves to detect an opponent floating in the sea or flying low, the detection performance may be compromised because radio waves create diffuse reflection when colliding with the sea level. 

However, The infrared sensor can detect targets that the radar has not yet picked up since it picks up the infrared rays that the target generates when the surface temperature rises due to engine or air friction.

But, since the basic detection range is short, it is usually used complementary to radar, and some warships do not have an infrared sensor.

Daring-class destroyer with high radar to detect even beyond the horizon

“The weapon system of modern warships”

1. Cannons

When a ship finds an enemy, it usually attacks it with guns, missiles, torpedoes, or depth charges. In the past, guns were the primary weapon of warships, but now, except for some high-speed boats, they are more of a secondary weapon.

20mm phalanx close air defense weapon system

 Warships mainly use guns to attack high-speed boats that are too small and fast to attack with missiles and torpedoes or fire threatening fire at their opponents. 

The larger the gun, the longer the range, the stronger the power, but the lower the rate of fire. Guns with a caliber of 100 mm or more are mainly used for a direct attack by enemy ships or for supporting friendly ground forces on the coast.

Anti-aircraft guns use guns with a caliber of 70mm or less to attack enemies in the air and on the water. When an enemy missile or plane is within 2 or 3 km, it is hard to shoot it down with missiles alone, so anti-aircraft guns are used.

2. Missile

Depending on the target, warships are equipped with anti-aircraft missiles, anti-ship missiles, and anti-surface missiles. Anti-aircraft missiles are missiles designed to intercept enemy missiles or aircraft. 


Short-range anti-aircraft missiles have a range of 10 km and medium-range of around 50 km and can intercept targets more than 100 to 200 km away. The longer the range, the larger the missile and the larger the radar and ancillary systems to operate it.

Anti-ship missiles are missiles designed to attack enemy ships. Worldwide, anti-ship missiles are operated as cruise missiles using jet engines.

 Anti-ship missiles of the cruise missile type increase their speed right after launch with a rocket booster. When the speed is high enough, the booster is taken off, and a small jet engine inside the missile is used to move it. Jet engines are often used because they use less fuel than rockets and can move missiles long distances.

Subsonic anti-ship missiles with a flight speed of Mach 0.8 and supersonic anti-ship missiles with a flight speed of Mach 1.5 to 3.0 are the two types of cruise missiles.

Subsonic anti-ship missiles are slow, but because of their small size, a single ship can carry several rounds, and their long-range allows them to attack enemies from a distance without revealing the location of ships.

Regarding intercepting anti-ship missiles, supersonic anti-ship missiles have the benefit of a short response time, even if the opponent detects them, due to their high speed.

ground-to-ground missiles strike targets on the ground. The majority of surface-to-ground missiles are jet-powered cruise missiles. The American BGM-109 Tomahawk, which gained fame during the 1990s Gulf War, is a ship-launched surface-to-surface cruise missile.

3. Underwater Weapons

RUM-139 anti-submarine rocket

A torpedo is a missile that travels through water. Since rockets or jet engines cannot be used underwater, torpedoes are powered by electricity or small engines to turn propellers. Torpedoes are divided into light torpedoes and heavy torpedoes according to their size.

Light torpedoes have minimal explosive force but are compact and agile. It’s used to attack submarines by warships. Submarines are vulnerable to light torpedoes. It can cause a significant amount of damage once it hits the submarine.


Submarines mostly use heavy torpedoes because they can sink major enemy ships because of their vast range and potent explosive power.


Depth charges are submarine attack weapons that do not have a separate guidance function. Instead, operators can program the depth charge to self-destruct when it reaches a certain depth before dropping it into the water.

If the warship detects the presence of enemy submarines nearby but does not know the precise location, it sets the depth charge to the depth at which the enemy submarines are most likely to exist and then drops it.

Depth charges are a low-cost means of delivering many projectiles to a specific location. The sub is doomed if one of the multiple depth charges carried by the submarine detonates nearby.

In addition, there are anti-submarine rockets as offensive weapons of warships. Around World War II, it was a method of launching a rocket by attaching a rocket to a depth charge.

 Modern anti-submarine rockets are a type of torpedo-launching missile. When fired at an enemy submarine 30 to 40 km away, it flies close to the target, and the light torpedo inside is separated. The detached light torpedo is acquired while slowing down using a parachute and then searches for nearby submarines with its sensor and, if found, follows them.

“Modern warship defense system”

Additionally, warships employ a range of defensive measures. For instance, electronic Counter Measurement (ECM) is utilized when an enemy-guided missile is in flight. This device, also known as a jammer, can broadcast erroneous radio waves to enemy radar-guided missiles, causing them to make loud noises or misfire.

In addition, it launches a chaff rocket, a weapon that scatters into the air small bits of fiberglass covered with a radio-reflective substance such as aluminum.

The fragments that reflect radio signals effectively are known as Chaff. The Chaff is invisible to the naked eye, yet it appears enormous on the radar. It can be used to make the enemy’s radar think that Chaff is a ship, or it can be used as a smoke screen to hide where a friendly ship is.

Active decoys driven by propellers or rockets reflect radio waves well or emit their own, making them look like big warships on enemy radar. Active deception can deceive the enemy radar precisely because it can move on its own, unlike the Chaff, which only floats in the air. 

Modern warships reflect fewer radio signals to the opposing radar for stealth. In this instance, it’s easier to shield friendly ships with ECM, Chaff, and decoy if the enemy detects them.

Enemy torpedoes in the water running towards the warship can also be deceived by the torpedo track. Since torpedoes usually use sound waves to detect ships, the torpedo decoy creates sound waves similar to those for friendly vessels to deceive enemy torpedoes. 

Self-moving torpedo decoys are like active ones. Some torpedoes mistake a stationary target for enemy deception and look for moving ones. Self-propelled decoys can deceive even these torpedoes and move the enemy torpedoes further away by moving in the opposite direction to a friendly ship.

Meanwhile, until around the Second World War, warships had thick armor plates on the deck and sides of their ships to block enemy shells, but modern warships rarely have such armor.

 This is because armor makes the ship larger and heavier, making it more vulnerable to attack from aircraft or missiles. Instead, there is a tendency to focus on the ability to quickly prevent and recover from additional damage (such as fire or explosion) even if it fails to intercept an enemy missile and is hit.

Good defense knowledge to know

1. Battleships, cruisers, destroyers, frigates, corvettes

A battleship is similar in meaning to a warship, but in military terms, it is a huge ship with several large-caliber guns and thick armor on the deck and sides of the ship. 

Spruance-class destroyer (left) and Ticonderoga-class Aegis cruiser (right)

The battleship has not been used since World War II. Cruisers, destroyers, frigates, and corvettes are named according to the size of each ship in that order. Until just before World War II, it was strictly classified according to the size of ships and the size of the mounted guns.

 The major countries pledged to manufacture warships and cruisers at an appropriate level by adopting a disarmament convention. Regulations were strictly enforced in an environment where everyone was watching each other.

Currently, there are no specific regulations, and the ship’s name is different depending on the size of the ship and the Navy of each country. For reference, the cruisers, frigates, and corvettes are each named after the ships in the days of sailing. 

A cruiser is smaller than the main battleship, but it is a sailing vessel that can operate alone, and a frigate is a small warship that is prepared for an enemy surprise attack from behind the main battleship. 

A corvette means a smaller sailing warship than this. Destroyer is a word that appeared in the 20th century.

2. Aegis

The United States had a strong aircraft carrier force during the Cold War, and the Soviet Union deployed supersonic bombers capable of firing many anti-ship missiles to counter this. 

The US judged it difficult to completely intercept Russian anti-ship missiles with only fighters launched from aircraft carriers.  So they developed a combat system specialized for intercepting air enemies, the Aegis combat system produced by Lockheed Martin in the United States.

It is named after the shield in the fire because its combat system protects the entire fleet, including friendly aircraft carriers, from air enemies. 

Many anti-aircraft missiles are part of Aegis’ arsenal, as are a strong radar, a system that automatically integrates and classifies surrounding data, and a huge computer for calculations. The radar monitors hundreds of objects within several hundred kilometers of the surrounding air.

 In other words, the Aegis warship refers to the entire ship carrying the Aegis warship rather than referring to a specific type of ship. The United States installed the Aegis system on Ticonderoga-class cruisers and Arleigh Burke-class destroyers, and Korea also installed the Aegis system on Sejong-class destroyers.

3. Aircraft on an aircraft carrier

An aircraft carrier can be thought of as an airfield floating on water. Aircraft can carry out their missions over much longer distances than warships. 

The presence of an aircraft carrier greatly expands the naval battlefield. Of course, modern warships are equipped with missiles, but there is a limit to the number of payloads, and since they are disposable, they cannot stay in the combat area continuously like aircraft.

In games and cartoons, the captain of an aircraft carrier gives orders directly to the aircraft pilots, but in reality, there is a captain who manages the ship and a commander who directs the aircraft units, so the captain cannot give orders directly to the aircraft units.

 All aircraft aboard an aircraft carrier are also part of the Navy. Aircraft carriers themselves rarely carry weapons and only have minimal defensive armaments.

 This is because it is more important to reduce space and weight to accommodate the aircraft and its necessary armaments and fuel. 

However, many other warships escort the carrier since an aircraft carrier is essential. Aircraft on board aircraft carriers are also tasked with protecting aircraft carriers and friendly fleets and attacking enemies.