Destroyer

The Destroyer is an on-surface vehicle type in Ironwolf. Currently, it is only encountered as an enemy in missions or open world, but there are plans for a player-controllable Destroyer. The Destroyer is a very capable and dangerous vehicle to the Submarine.

Appearance
The Destroyer can easily be identified by its 3 smoke stacks and relatively large size.

Equipment
The Destroyer is equipped with multiple dangerous tools & weapons.

Naval Guns
Naval Guns will fire at the Submarine when it is surfaced. They will fire as soon as the target is in 1500 meters of the Destroyer. These deck guns have a low travel time and do a large amount of damage to the submarine. It is not advised to fight the Destroyer while surfaced.

Sonar
The Destroyer has a front-mounted Sonar location system. When the Destroyer is aware of the Submarine's presence, it will start sending out waves of sonar visible on the captain's map. It will send these waves of sonar down diagonally from the front of its bow. The sonar will go over the submarine when it gets close enough, leading to the submarine being lost and the Destroyer assuming the depth it was last seen at is its current depth (for deploying depth charges).

Sonar can also be avoided by resting the submarine on the seabed. Depending on how deep the seabed is, this can be a very dangerous maneuver to resurface from.

Depth Charges
Depth Charges are used by the Destroyer to attack submerged targets. Depth charges are configured at a certain depth - this depth is decided by the last visible sonar location of the submarine. If the player is far under the depth of where the charges are set to go off or relatively far above them, they can be avoided and will not deal damage to the submarine.

Health, weak points
The front half of the Destroyer's bow needs 8 hits for it to be sunk. The rear half of the bow needs 5 hits for the Destroyer to be sunk. There's a weak point on the rudders & propellers on the rear of the ship, but these are very difficult to hit as the Destroyer will start turning to face the player as soon as the Destroyer is aware it's being attacked.

In most cases, the Destroyer will need 2 torpedo volleys to be taken out.

Naval Gun Attack (Surfaced Submarine)
As soon as the submarine is in firing range (1500m) of the Destroyer, it will start firing it's naval deck guns at it. They deal a lot of damage and fire in rapid succession, so it is recommended to never get in 1500m range of the Destroyer while surfaced. The Destroyer will keep a firing distance, but will not attempt to go past the submarine like in its anti-submarine strategy below.

Depth Charge Run (Submerged Submarine)
If the Destroyer catches wind of a submerged Submarine, it will use sonar to locate the submarine. It will send out waves every few seconds and depending on whether the wave hit the player or not, there'll be an audible "ding". As soon as the first sonar wave finds the submarine, the Destroyer will start driving towards it. As soon as the Sonar goes over the submarine and the Destroyer has lost contact/location, it will remember the depth at which it did and then deploy depth charges when it goes over where it last saw the submarine. These can be avoided if depth is changed after sonar contact is lost. The Destroyer will then drive on for another kilometer or so and turn around when/if it notices the submarine again after which it will repeat the same strategy.

References:

 * Kongsberg for naval sonar
 * https://www.kongsberg.com/maritime/products/naval-systems/ASW/