Destroyer

A destroyer is a type of warship, the nature of which has evolved since it first came into use, roughly at the beginning of the twentieth century. Several other warship designations have, at different times and in different navies, overlapped the "destroyer" role. Most common among these roles are cruiser and frigate. Another type of vessel, whose nomenclature is the root of "destroyer", has been called "torpedo boat" and exists in new forms.

Initial usage

When the modern self-propelled torpedo was invented, in 1866, by Robert Whitehead, it was initially added to conventional warships, but navies soon realized that a small, fast craft, with a main battery of torpedoes, could threaten much larger warships such as battleships. The battleship of the early 20th century was the largest, most heavily armed, and most heavily protected warship type, but relatively slow and not extremely maneuverable. Torpedo boats were generally not capable of long-range steaming or being seaworthy in the "blue water" deep ocean; they were coastal craft.

When battleships and other large ships, possibly escorting unarmed cargo and troop transports, needed to approach a hostile shore, they needed to deal with the torpedo boat threat. A partial solution was adding a secondary gun battery of smaller caliber, faster firing rate, and faster aiming than the main guns intended to sink other battleships, but the secondary battery still let the torpedo boats come too close.

A new type of vessel, called the torpedo boat destroyer, was developed as an escort to major warships, and possibly merchant vessels threatened by torpedo boats. In the words of a requirement restated a century later, "Self-deployability (blue water endurance) is needed to allow the platforms to get to the contested area without the need for valuable and scarce open ocean transport or the support of an ever-present mothership." Such vessels still had to be small, fast, and maneuverable enough to pursue and destroy torpedo boats.

First evolution

It soon became obvious that the torpedo boat destroyer was a useful vessel for a wide range of applications, such as convoy escort, so the specialized designation became the simple destroyer. Ironically, while the first destroyers were armed only with quick-firing guns, usually of several calibers from medium to light, navies started equipping destroyers with torpedoes, as the weapon of choice if they did need to confront battleships. For simplicity, the category of "cruiser" is not being included in this immediate discussion; simply assume they were vessels of intermediate characteristics between battleshps and destroyers.

First World War, and a new torpedo threat

The pure torpedo boat was becoming less popular around the start of the First World War, although variants would keep returning. Torpedoes, however, were still a real threat, but from submarines rather than surface vessels.

Technology for finding submerged submarines lagged the introduction of the undersea weapons, and was quite primitive and short-ranged. In general, the first antisubmarine sensors were passive listening devices, called hydrophones. Putting hydrophones on many destroyers allowed an antisubmarine screen to be formed around the "high-value assets", the vessels the submarines had as primary targets.

Once a submerged submarine was located, location being a very loose term at the time, the destroyer needed some way to attack it. Clearly, guns that could blow a surface torpedo boat out of the water were not the answer, since they cannot shoot at underwater targets. The first antisubmarine weapons were depth charges, or containers of explosives that would be dropped, from the surface, over the location of a suspected submarine, and would detonate when they reached a preset depth. The submarine's depth was even harder to determine than its range and bearing (distance) from the destroyer; it was estimated based on the strength of the sound, knowledge of the bottom depth and water characteristics, and a seaman's judgment. Since the submarine's position was poorly defined, large explosive charges were needed to have a chance of danage with other than a lucky direct hit.

By 1918, however, an active sound-based technique, code-named ASDIC for an apparently nonexistent "Allied Submarine Detection Investigation Committee" was mounted on several British and U.S. destroyers. It came too late for combat use in the First World War, but development actively continued. The more common term became sonar, for "sound detection and ranging". In modern intelligence terminology, active and passive sound-based systems were the acoustic MASINT or acoustic intelligence of geophysical measurement and signal intelligence.

Yet more torpedoes, and things that carried them

By the Second World War, aircraft could drop torpedoes, as well as use weapons including machine guns and bombs. In its evolving role as an escort, as well as being a general-purpose craft for independent assignments, the destroyer now needed to add anti-aircraft warfare to its anti-submarine warfare and anti-surface warfare roles.

Often, the generic radio call sign for U.S. destroyers was "small boys". Indeed, destroyers were small beside the aircraft carriers and the impressive but obsolete battleships. Arleigh Burke, a noted destroyer unit leader in WWII, is, ironically, the namesake for today's Burke-class destroyers. When a Burke-class vessel can shoot cruise missiles at land targets 1000 miles away, fire surface-to-air missiles at aircraft 100 miles away (and tracked farther away), and even may "shoot a bullet with a bullet" in ballistic missile defense, the small boys have grown up. There are, however, emerging new warship types that may take on the role.

Antisubmarine evolution

Destroyers now were the primary antisubmarine warfare weapons, with active sonar as their primary sensor, supplemented with passive listening, and radar detection of surfaced submatines. Particularly in the Battle of the Atlantic, submarine hunting also had the benefit of national-level intelligence information, including signals intelligence from German fleet headquarters to submarine radio, including direction finders aboard warships. Very long range patrol aircraft also could spot submarines.

The depth charge was still the primary antisubmarine weapon, although more flexible launchers were developed. Previously, they were rolled off a rack at the stern, but devices such as "K-guns" allowed the depth charges to be thrown to the sides of the destroyer, allowing circular patterns to be dropped. Depth charges had the disadvantage of creating great disturbance in the water after they exploded, making sonar useless until the water calmed, and possibly letting the submarine escape in the noise.

"Hedgehog" used a very different method, of a number of small charges launched straight ahead of the submarine, which made the approach to the target more intuitive."...if they used a missile that only exploded if it hit the target, they could afford to cut down the weight very significantly." Hedgehog used an impact, not a depth, fuze. If there was an explosion in the water, it confirmed the existence of a submarine, gave a good position fix, and damaged the target. Even a small leak could force a submarine to the surface, where it was at very great disadvantage in a gunnery engagement with a destroyer.

Over time, it became apparent that there were really two antisubmarine escort missions. Destroyer speed was still needed when escorting major warships, but merchant convoys were much slower. Depending on the theater of war, the surface and air threats to merchant vessels might be much less than to a battle fleet or invasion force. These observations led to creating smaller variants of destroyers, with smaller engines, perhaps 3" rather than 5" main guns, and fewer antiaircraft guns.

Such vessels still needed the same sensors as the full-sized destroyer, but the sonar might even be more effective due to the reduced engine noise from the smaller engines. The U.S. name for these was "destroyer escort", and other navies might call such vessels "sloops" or "corvettes" or "frigates". They needed a smaller crew, and were faster and cheaper to build, just what was needed for convoys needing many escorts.

General detection

radar

Antiaircraft evolution

Aircraft, with ever-increasing performance, were more and more of a threat. The initial machine guns quickly proved to have insufficient range and stopping power to be useful, although some .50 caliber or comparable heavy machine guns were retained for final use, and perhaps for attacking boats or to threaten ships with little or no armament. Against non-kamikaze aircraft, the various weapons systems had significantly different effectiveness While some earlier studies showed the .50 caliber as having shot down some aircraft, serious analysis showed that the 20mm Oerlikon autocannon was the lightest weapon with significant kill probability.

Rounds needed to shoot down non-kamikaze aircraft

#aircraft	20mm Oerlikon	40mm Bofors	5"/38 non-proximity	5"/38 proximity fuze
41	30,100	4,500	1,000	550

None, however, were as great a threat as the Japanese kamikaze, essentially the first autonomous anti-shipping missile. The guidance system of these missiles, however, was not electronic, but a human pilot who would die as he crashed the aircraft into its target ship. It was no longer enough to disable the aircraft a distance away from the ship; the destroyer had to force the kamikaze to crash into the sea. Once the kamikaze was in the final approach, even killing the pilot might not stop it from hitting; the final defense had to have sufficient energy to divert the aircraft from its final course.

Rounds needed to shoot down kamikaze aircraft

#aircraft	20mm Oerlikon	40mm Bofors	5"/38 non-proximity	5"/38 proximity fuze
24	27,200	6,000	1,000	200

The problem was not firepower alone, but also fire control. Ideally, a destroyer could engage kamikazes with 5" guns, equipped with proximity fuzes. These guns had the greatest range and killing power, and best integration with the CIC and radar.

Surface warfare evolution

Torpedoes remained the destroyer's principal weapon against large ships. Most often, they were released from deck-mounted horizontal launchers that could usually be trained in azimuth, but some destroyers had fixed bow-facing torpedo tubes that were aimed by aiming the ship. The Japanese Type 93 or "Long Lance" torpedo was greatly ahead of the torpedoes of other navies. All surface torpedoes of the war had no active guidance, although they did have stabilization systems to keep them straight-running.

At the start of the war, Japanese destroyer doctrine for employing torpedoes also was superior to those of other navies, as demonstrated at the Battle of the Java Sea.

5" guns were effective against smaller vessels, and even the secondary autocannons could be useful against boats, or a surfaced submarine. Ramming remained as a last resort.

Technological and doctrinal evolution

Japanese torpedo warfare dominance waned, at least in night actions, when they remained principally dependent on optical sighting rather than radar.

Especially when making torpedo attacks with a unit of destroyers, some navies found it useful to have a heavier ship in the unit, both as the command vessel (i.e., flagship), but also to support the other ships with heavier fire or better sensors. This role was not infrequently assigned to a light cruiser, but the "destroyer leader" type also emerged. After the war, the U.S. Navy had a confusing period when it reclassified its destroyer leaders (i.e., heavy destroyer) as "frigates", when the more common usage of frigate is for vessels lighter than destroyers.

Destroyer in notable WWII surface actions

Battle of Narvik

HMS Glowworm' vs. SMS Hipper

Battle of Leyte Gulf

Small boys or not, sometimes one must grow up very quickly. Some boys aged very fast at the largest naval engagement in history, the Battle of Leyte Gulf.

The old torpedo boat destroyers were meant to protect battleships, but, at the Battle of Surigao Strait, roles were reversed. U.S. PT boats harassed a Japanese battleship task force, but then squadrons of destroyers swarmed in with torpedo attacks, blowing IJN Fuso in half, and crippling IJN Yamashiro to be sunk by U.S. battleships. Some of those battleships, in the last battleship vs. battleship engagement there was ever to be, had crawled out of the mud of Pearl Harbor to take their revenge — after the boys had softened the opposition for their fathers.

In what has been called the most gallant action in the history of the U.S. Navy, the Action off Samar during the Battle of Leyte Gulf, communications errors and wishful thinking on the part of a senior commander left a small force as the screen between the vulnerable transports of the invasion force and a powerful Japanese surface force led by the world's biggest battleship, IJN Yamato. Seven destroyers and destroyer escorts, with backup from aircraft not armed for attacking warships, challenged four battleships, eight cruisers, and eleven destroyers &mdash and turned the Japanese force back, sinking three heavy cruisers and badly damaging another, and protecting the landing force. USS Hoel, Johnston and Samuel B. Roberts sank and the other four were seriously damaged.

Information-centric warfare

Still in WWII, the destroyer, along with other warships, began to regard information as a weapon. The captain of a destroyer might be more effective in combat not on high on the bridge, relying on his eyes and ears, but in a combat information center, where lookout reports, sonar, radar, radio messages, and other data could be fused onto tactical charts.

The dawn of guided missiles

Destroyers and cruisers were the first warships, in most navies, to be equipped with guided missiles. The initial installations were usually surface-to-air missiles, sometimes with a secondary surface attack capability.

Dedicated surface-to-surface missiles (SSM), specifically anti-shipping missiles intended for use against targets surrounded by water, revived the concept of the "eggshell with a sledgehammer", or small fast vessel with a powerful offensive weapon. In the revival, however, the sledgehammer was the naval SSM.

In the first combat use of an anti-shipping SSM, Egyptian Osa-class missile boats, of Soviet design and construction, sank the Israeli Navy flagship, the destroyer Eilat during the 1967 Arab-Israeli War. The Osas used P-15 Termit (NATO reporting name SS-N-2 STYX) missiles.

Designation confusion

Between 1950 and 1975, there was much changing of ship designations, which, for a time, led to a perceived "cruiser gap" between the Soviet Union and the United States. In reality, there was no gap, but the frequently changing names of ship types affected destroyers as well.

One particular class, or pair of classes depending on how they are defined, were called "destroyer leaders": the Farragut/Coontz class. On 30 June 1975, these were reclassified as guided missile destroyers (DDG), where the other "frigates", the term being used for a warship intermediate between traditional destroyer and cruiser sizes, became guided missile cruisers (CG/CGN).

During this time, that which had been called a "destroyer escort" during WWII kept the DE designator, but was renamed an "ocean escort". In June 1975, the "ocean escorts" of the Perry, Brooke, Knox, Garcia, and Bronstein Classes, changed name and designation to frigates (FF).

Modern destroyers

Even now, the role changes. A Burke-class destroyer of the U.S. or Japanese navies still has a 5" gun and smaller autocannon, but its main battery is a vertical launch system that can fire a variety of precision-guided munitions. The latest "flight 2B" Burkes also have a pair of helicopters, and the AEGIS battle management system. The vessel has the displacement of a WWII light cruiser.

In a number of respect, the Burkes, especially the later "flights", were to "wfix things that were perceived to be wrong with the CG 47. Specifically, it was felt that a ship armed with Tomahawk, unlike a carrier escort, could fight while hurt. Even if the ship were slowed and had lost a combat system capability in one or more areas, if it could receive Tomahawk targeting data and launch, the self-guiding missile would be fully functional. Thus the DDG received a steel superstructure, increased blast overpressure resistance, more armor, a collective protection system and radar cross section reduction measures. Thus there is a historically anomalous situation of the destroyer being a more survivable ship than the cruiser. "

Anti-air warfare (AAW)

This is the most potent mission on modern destroyers, although its surface-to-air missiles usually have a secondary surface-to-surface capability, and the same launchers used for the SAMs can fire purpose-built surface-to-underwater missiles and surface-to-surface missiles.

With respect to the Burke vs. Ticonderoga situation, the Ticonderogas had not only more VLS tubes, but also had additional AN/SPG-62 terminal illuminators.

Anti-submarine warfare (ASW)

Given that the most potent torpedoes are now on submarines, not surface ships, a destroyer will want to engage a submarine at a considerable distance. If the destroyer carries an antisubmarine helicopter such as the SH-60 Oceanhawk, the role of the ship may be to support the helicopter, with sensors and refueling. The kill mechanism would be lightweight torpedoes dropped from the helicopter.

If the destroyer has a long-range surface-to-underwater missile (SUM), such as the Russian RPK-2 Viyuga (NATO designation SS-N-15 STARFISH, that will fly through the air and drop a homing torpedo in the predicted vicinity of the submarine, it may be just as much a threat as the helicopter. Indeed, the helicopter may emphasize its sensors for finding the submarine and letting the destroyer's SUMs kill it.

Destroyers have non-missile carried torpedoes, but these are last-resort weapons, generally to kill a submarine that has already fired torpedoes that will kill the destroyers. The new Russian torpedoes of extremely high, even supersonic, speed may put a new dimension on this tactical scenario.

Anti-surface warfare (ASuW)

Different navies give their destroyers different priorities. The later Burke class have done away with their pure Harpoon anti-shipping missiles, but the Russian Sovremenny class and the Chinese equivalent carry the very potent Moskit (NATO designation SS-N-22 SUNBURN).

Although its mission is no longer primarily surface warfare, it could give a WWII battleship a very hard time with its RIM-66 Standard missiles in surface-to-surface mode, using over-the-horizon targeting. A 13.5" diameter missile, of a weight depending on how much fuel it consumed, traveling at Mach 3.5, would have more kinetic energy than a traditional battleship shell, to say nothing of a substantial high-explosive warhead and burning fuel.

Support to land operations

• cruise missile
• new generation guns, including advanced gun systems and futures such as vertical gun systems and railguns

Where do new types fit?

New vessel types are both larger and smaller than current destroyers. The large vessels arguably could be called cruisers, while the smaller ones really do have some different missions for which no ship had been designed.

Zumwalt class

Zumwalt-class destroyers are the U.S. Navy followon to the Burke class. They have grown to 14,000 ton vessels. From the standpoint of size alone, it would not be unreasonable to think of such a vessel as a cruiser of quite substantial size. Under current U.S. definitions, however, a cruiser has a major area air defense capability, but the Zumwalts are optimized for land attack.

Purely for land targets, especially for fire support to ground forces ashore are two 155mm Advanced Gun Systems (AGSs), fed from automated magazines. While early reports suggested that the 155mm caliber, not previously used in U.S. naval guns, would have advantages through commonality with the standard 155mm land howitzer caliber, current thinking is that very little will be alike. The AGS will have two basic kinds of ammunition, one being a long-range precision-guided munition for which there is no equivalent ground forces requirement.

If there is any sharing, it will be in the conventional munition rounds. A current 155mm howitzer, the U.S. M109 used by many countries, has a basic maximum range of 22km; 30 km with rocket-assisted projectiles. Given the current concerns about the hazards of the littoral, how close to shore will one of these large vessels come? Remember, that 22 km range is fron the ship to the target, not the shore to the target.

The long-range systems of the Zumwalt will, like the Burke, be its vertically launched missiles. Her Advanced Vertical Launch System (VLS) can use BGM-109 Tomahawk cruise missiles, long-range RIM-156A Standard SM2-MR Block IV surface-to-air missile (SAM) with a secondary anti-shipping (SSM) capability, shorter-ranged RIM-162 Evolved Sea Sparrow Missile (ESSM) also with SAM and SSM capability, and RUM-139 VLS Anti-Submarine Rockets (ASROC).

There a pair of 40mm Close-In Gun Systemsfor self-defense against air and sea threats.

Littoral combat ships

under names such as littoral combat ship and "Streetfighter", roles are being defined for smaller vessels that may be the "small boys" of the future. These boys will play in a different neighborhood than their fathers and grandfathers, who were designed to operate in the "blue water" of the deep ocean. Coastal areas, with confined areas such as the Strait of Hormuz, Strait of Malacca, and Taiwan Straits, form the "green water" littoral, with different requirements for sensors and weapons.

As the first torpedo boat destroyers needed to be "self-deployable", so does the Littoral Combat Ship. The LCS, however, has a much wider range of potential missions than did a pure torpedo boat destroyer, including:

• antisubmarine warfare: with the special considerations of detecting quiet submarines in the difficult acoustic conditions of the littoral
• mine countermeasures: Again, finding mines is much harder on a cluttered, rocky shallow bottom than in deep water
• anti-surface warfare: The threat here is not only from conventional naval vessels, but also from explosive-laden small boats, with a crew prepared to die, such as the 2000 attack on the USS Cole. Suicide attacks are not the only threat; missile boats can be concealed along the coast, rush out, and fire at short range.
• naval special operations support: "mothership" for special reconnaissance, raids, deception, placement of intelligence sensors, etc., by specialists such as the British Special Boat Service, U.S. Navy SEALs, etc.
• Non-combatant evacuation operations / Humanitarian Assistance / Medical support
• Boarding and inspecting ships
• Security survey prior to arrival of large forces