Yes, at first glance everything is clear - ships theoretically differ in displacement, armament, size, tasks ... This is theoretically. But in practice ...
But in practice, there is a world naval mess. In general, the phenomenon on the waves is thoroughly mundane and familiar, approximately like an evil boatswain at the morning formation.
And it turns out that, in fact, there is no clear definition of classes as such! Not at all!
Here is an example of the well-known type "Arlie Burke". Full displacement of 9 tons. This is a destroyer.
Here is his opponent, "Sarich". Also a destroyer. Full displacement under 8 tons.
And here is the Iranian destroyer Jamaran of the Moudge class.
And its displacement ... 1500 tons! That is, it seems to be a frigate or even a corvette, but in Iran these ships are called destroyers!
There is "Zamvolt" with its almost 15 tons of displacement. There is a Chinese Type 000 with 055 tons. It is being built so far, but it will be built.
And if to add to this squadron the idea of the destroyer of Project 23560 "Leader", the displacement of which was close to 19 tons according to the papers ...
That is, whoever wants what, creates it.
With frigates, too, everything is not so simple, this is generally, probably, the most controversial class in ocean waves. It is enough to remember where it came from in general. From the French, who invented this small but nimble ship with one (later two) gun deck to fight pirates.
Since the frigate was mainly engaged in patrol service, reconnaissance, escort of merchant ships and raider service, which was then called cruising. And so it happened that some of the frigates, in fact, became cruisers. And when they received steam engines, towers and armor, they became first steam frigates, and then official cruisers.
The gun deck is a thing of the past, and with it the very concept of a frigate disappeared around the end of the 19th century and did not appear until the mid-20th.
But at this time a destroyer appeared.
Small but very nasty ship with self-propelled mines and later torpedoes. And later, destroyers appeared, larger ships, with stronger artillery, whose main task was to sink destroyers, protecting squadrons of large ships from them.
And during the Second World War, frigates appeared again. They were returned by the British, who were forced to come up with a new class of ships to protect the convoys.
The new frigate was not as well armed as the destroyer and was smaller. But this ship was larger than a patrol boat, and could escort transports across the ocean. And his weapons were enough to fight off the German planes, and - most importantly - to drive away the submarines from the convoy, which at that time were a real scourge of God for Great Britain.
It turned out to be an intermediate class between destroyers and patrol boats, in fact - an anti-submarine defense ship.
During the war, the Americans had their own ships, similar in characteristics to British frigates. They were assigned to the subclass of destroyers: DES - Destroyer Escort Ships - escort destroyer.
After the war, they were reclassified as ocean escorts, since before the 1975 reclassification "frigates" were called light missile cruisers built in the size of destroyer squadrons. And then the Americans went over to the British classification system.
Indeed, the British frigate was between the destroyer and the boat, and the American one was between the cruiser and the destroyer. And NATO demanded at least approximate uniformity.
Today, the line between frigate and destroyer is gradually blurring. In general, the destroyer is still slightly larger than the frigate, armed with a bit heavier, possibly faster.
If we take as an example the old destroyer of project 956 "Sarych" and compare it with the frigate of project 22350 "Admiral Gorshkov", then the displacement of "Sarych" is more than a frigate, 8 tons versus 000 tons. The speed is also higher for the destroyer, 5 knots versus 400 for the frigate. The range of the ships is about the same, about 33 miles.
Frigate "Admiral Gorshkov"
But in terms of weapons, everything is not so simple.
The artillery armament is stronger on the destroyer. 2 gun mounts AK-130 (4 barrels 130-mm) against one 130-mm mount A-192M.
Anti-aircraft artillery is stronger on a destroyer. 4 x 6 x 30 mm ZAU AK-630 versus 2 x 1 x 30 mm ZAK "Broadsword".
The frigate's anti-aircraft missile armament is better, the Redoubt is definitely better than the Hurricane (this is the naval version of the Buk). The destroyer has more missiles in a salvo, but still the Redoubt is a new generation.
Well, the main armament of the ship is tactical missile. 2 x 4 anti-ship missiles P-270 "Mosquito" at the destroyer against 2 x 8 "Onyx", "Zircon", "Caliber" at the frigate. And in the future, the next models will have 4 x 8, that is, 32 launch cells.
Well, let's be honest - "Mosquito" is outdated for a long time. And even if you replace it with something modern, the frigate still has more "trunks".
The frigate's mine and torpedo armament is also better.
In general, it is clear that today the new frigate is much more efficient than the old destroyer. In addition, frigates are somewhat cheaper, although this has always been the case. This made it possible to stamp frigates like pies.
It is worth looking at the experience of the PRC here. The Chinese significantly spread between two classes of ships. Destroyers of type 052D "Kunming", which form the basis of the naval strike forces, have a displacement of 7500 tons and carry weapon in 64 PU.
Frigates of type 053N3 "Jianwei-2" are much lighter (2500 tons) and carry weapons to a minimum, like normal frigates: 8 launchers for anti-ship missiles and 4 launchers for air defense systems.
Approximately the same weight distribution in Japanese fleet... Only frigates of the "Abukuma" type, of which there are only 6, are even lighter in armament than the Chinese ships. Well, the Japanese destroyers, that "Congo", that "Atago", they are generally related to "Arleigh Burkam".
The difference between the classes, oddly enough, today is beginning to fade. It has already been said on our pages that Arlie Burke is ¾ Ticonderogi, and if you take and put next to the American cruiser a new Chinese destroyer of Project 055, it will become clear that the cruiser is very light (9 tons), or the Chinese destroyer was fed (800 tons). But the cruiser is smaller than the destroyer - it somehow does not fit into the picture.
Roughly the same thing will happen in the class below, where corvettes (for example, the corvettes of the project 20385 of the "Guarding" type) are quite stepping on the heels of the frigates. The same 2 tonnes of displacement, the same 500 cells for launching anti-ship missiles of the type "Caliber", "Onyx", "Zircon", the same "Redoubt" as air defense and so on.
And such a corvette can easily pile on another frigate one on one. Or the Iranian "destroyer", if it turns up under the stem.
Excuse me, but where is the difference then?
In an amicable way, there are only two classes of ships in the ocean zone in the world, in addition to aircraft carriers. These are large ships (cruisers, destroyers) and small ones (frigates and corvettes). Roughly speaking, how not to recall the classification of the Soviet fleet, where there were ships of 1 and 2 ranks.
And there are not so many cruisers as such in the world. Seriously though, 2,5 Russian heavy cruisers, 3 missile cruisers and 22 American Ticonderogs are, in general, all cruisers for today. Not so many, and given the more than veteran age of the cruisers, it can be assumed that in 10 years only a few will remain from this detachment.
And the main force (I do not take into account aircraft carriers) in the majority of the world's decent fleets will be the destroyer. Which will not be inferior in its capabilities to cruisers. The same 112 UVPs of the Chinese "Type 055" are not much inferior to the 122 UVPs of Ticonderogi.
In general, the cruisers will go to history, as once their linear relatives left, and then the ships of the line.
The main striking force at sea will continue to be an aircraft carrier and a destroyer that has mutated to the size of a cruiser. And as cover ships and various escort operations (and drive pirates) frigates and corvettes will work, which will obviously also merge into one class.
At least today it becomes very difficult to distinguish a frigate from a corvette. But this is a topic for another conversation.