I no longer have access to the Admiralty, so this question falls to the Dope. Recent warships don’t seem to have guns aft; only to the fore. Sample pic. Ships can’t turn very quickly, so why don’t they still have aft guns so they can engage targets in that hemisphere?
Missiles - the modern warship’s primary weapon - shoot in all directions.
The guns are no longer primary weapons, as Alessan said, it is all about missiles (and torps) now. Remaining guns are for shore bombardment and threatening pirates/civilian ships if needed.
I should add, small guns like the Phalanx systems are of course on board for close defense.
It is also difficult to have an aft gun with a flight deck and hangar. If you put it behind the flight deck then it gets in the way, if you put it on top of the hangar then it protrudes into the hangar space. So you end up with it amidships somewhere which reduces its field of fire anyway. And having a helicopter is massively more useful than another gun.
There is also no real need for he extra weapon, a single gun has a higher rate of fire and is more accurate these days.
The space a the stern end is usually reserved for a hanger and helipad, which is useful for all sorts of tasks such as seagoing resupply as well as airborne ops. The top of the hanger generally used for other systems which would include AA missiles, smaller caliber weapons such as Bofors and Oerlikons, or maybe a Phalanx installation. The hanger roof is not strong enough to support a full size naval gun, and anyway the auto load mechanism that feeds it takes up a couple of decks worth of space underneath it.
The missile-era, 1960’s, USN Belknap class (originally called ‘frigates’, later designated ‘cruisers’) had their 5" gun plus helo deck and hangar aft with Terrier (later Standard) AA missile system forward. This worked out probably because of the length and space requirements for the Terrier system, missiles stored in horizontal ‘ring’ magazine v that of 5"/54 gun, more favorable to use the bigger space forward for the missile system. Although the immediately previous class fit in two Terrier systems w/ no 5" gun or helo hangar. And obviously a helo deck/hangar should be aft so the helo’s can approach from aft along the ship’s length. The more recent (still in service in some navies) FFG-7 class of frigates (different definition than original one for Belknap’s) also had the main AA/antisurface missile launcher forward, 76mm gun amidships, relatively large helo facilities aft.
Recent shipboard AA missile systems generally have the missiles held (and launched) vertically so are relatively easier to fit where ever including along with helo facilities aft, and putting missile launchers fwd and aft diversifies in case one set of launchers is disabled. Then the space for a medium caliber gun usually opens up forward.
But there are also various examples of destroyer type ships with heavier gun armament aft than forward in the pre missile era also. Most of the Japanese destroyer classes of the 30’s were arranged that way; some German torpedo boats (as in small destroyers, not motor torpedo boats aka S-boats) of immediate pre-WWII had a 100mm gun aft but only light AA forward, etc.
Why is this obvious?
I don’t know anything about helicopters or ships, so ,yeah, I need some ignorance fought.
Helicopters are pretty versatile and maneuverable. I presume that while landing on a moving ship, the copter matches its horizontal speed to the ship, and then lowers itself down.
Why do that only on the aft side? --why can’t they do it anywhere on the ship?
I assume because that would entail either the helicopter flying into the wind and unable to see the ship on which it’s trying to land (because it’s behind it) or flying backwards.
It seems to me it’s just easier if both the boat and the aircraft are moving in the same direction.
Ship design usually dictates a high, sloping bow section, tapered to better cut through water/waves. Take a look at this profile:
Helicopter landing pads nice to be flat and wide, with a hanger adjacent. You also want them close to the waterline to minimize effects from the ship rocking side-to-side.
Forward looking visibility is also desired- a big bulky helicopter hanger on the front of the ship is going to obstruct that.
So the front of the ship is pretty much out. You definitely don’t want it in the middle of the ship either - for safety reasons you want to minimize the amount of obstructions on approach. So that leaves the aft.
If you approach the ship from abaft, you don’t have anything to hit if you miss the landing a bit. Ships will also (when possible) turn into the wind when landing a helicopter as well. Minimize the things that have to be compensated for and everybody is happier.
Besides answers already given, it is true that not a few offshore support vessels have helicopter decks above the deck house forward, such as this one
But that would be a big obstruction for a warship. And if the landing pad were on main deck level forward it really would harder to land, since coming in from the unobstructed forward direction the helo would have to move backwards when over the pad to synchronize speed if the vessel was moving forward. Coming onto an aft pad from aft it’s synchronizing a slow forward speed. Helicopters can go backwards but forward is more normal. And coming from aft then holding position far above a fwd deck level pad while descending past masts and superstructure I think qualifies as obvious in being more difficult. There have been naval support vessels, not outright warship I can think of, with amidships helo decks because there wasn’t room aft. And, obviously, full flight deck vessels can take on helicopters anywhere on deck.