What are destroyers used for?

Answer 1

When warships evolved from sail, wood and side mounted cannon to propellers, armor and turrets this made warships much more expensive then before. To destroy a warship you needed a gun big enough to break through its armor which required a bigger ship to hold that gun, bigger engines to push that ship and armor to defend that now very expensive ship.

Looking for a cheaper option of getting explosives reliably to the enemy ship than building another big ship to shoot them at it the self propelled torpedo was invented, a bomb with a motor that did not need a big gun to fire it. These could be mounted on small fast boats that survived by evading fire from bigger ships. Thus the Torpedo Boat was born.

To defend the big ships the Torpedo Boat Destroyer was invented. It was large enough to carry the fuel needed to sail long distances with Battleships and Cruisers, fast enough to find and chase down Torpedo Boats and had enough small guns to sink them. Since Torpedo Boats were small and thus didn't have a long range or stability on the high sea's Torpedo Boat Destroyers were the perfect new platform in which to carry Torpedoes in a fleet and became in addition Torpedo Ships themselves.

Their name was soon shortened to Destroyers whom would both defend their fleets from both Torpedo Boats and Destroyers and attack enemy fleets. At the time they were about 500-1000 tons, between 50-90m and relatively cheap to build. A new innovation in their old enemy the Torpedo Boat was the ability to submerge underwater and by the start of World War One the cheap Destroyers got the role of finding and eliminating these adding depth charges to their arsenal.

Near the end of and after World War One the threat of air dropped bombs became an apparent and growing concern so Anti Aricraft Weapons were added. In a race between nations to build the better Destroyer more firepower was added, more torpedoes, more naval artillery, more AA guns, more depth charges and with this a bigger hull to fit all that on, crew to operate it and bigger engines to keep the ship fast. They were now about 2000-3000 Tons and 100-130m long.

By World War Two they had become nearly as big as Light Cruisers in the last war so smaller Corvettes, Frigates and Destroyer Escorts were created to do most of the Convoy jobs of the old Destroyers while the new more expensive Destroyers stayed with main fleets. The WW2's Destroyers requirements at this time was having between 3-6 Naval Guns of about 4-6", ASW Rockets and Depth Charges, Scouting ability with Radar and Sonar, 1-3 Anti-Ship Torpedoes Batteries, a ring of AA Guns and a top speed of about 34-39 knots.

After the war when air power outstripped naval gunnery Destroyers became more about anti sub and anti aircraft duty. They again increased in size to accommodate Helicopters and new weapons like the ship to ship and ship to air missiles that were developed on and popularized during the Cold War. Now they are 5000-10000 Tons and 140-160m long. Frigates became about the size of WW2 Destroyers and Destroyers became about the size of WW2 Cruisers.

Destroyers went from a singular focus to the ship that does it all and as new weapons are invented they will most likely be added making them even bigger in the future. Case in point the 180m long 15000 Ton Zumwalt class Destroyer which is likely getting Railguns.

Answer 2

Yes. Destroyers still have a use in the fleets of today. They serve a number of purposes, including the duty of protecting the air craft carriers against submarine attacks. They provide gunfire support for troops on the shore and have anti-aircraft and anti-ship abilities as well.