Most engagements in Defcon are decided either directly or indirectly at sea. The player who has naval dominance is able to launch submarine attacks and carrier-based bomber attacks with impunity while being able to shoot down incoming enemy fighters and bombers with his battleships. If the two players are separated by an ocean, the player with naval dominance can almost completely deny the opponent of any scouting while being able to scout out the entire enemy territory himself.
The player who does not have naval dominance is forced to reconsider his strategy. Without scouting, his best strategy for inflicting megadeaths is launching all of his nukes simultaneously. Doing so will however place him at the mercy of enemy subs and bombers which are waiting at the coastline. Without a naval presence, the player will find his options limited at best.
Naval units in defcon follow a rock paper & scissors pattern. Battleships beat carriers, carriers beat submarines and submarines beat battleships. This pattern is complicated by the presence of carrier-based aerial units. Battleships are good at shooting down fighters, but are vulnerable to bomber fire.
The battleship picket lineEdit
In a straightforward 1v1 engagment, battleships are best kept in groups of two or three at the front line. Place some battleships at Defcon 5 to extend the range of your shore based radars, but do not lay out all your forces. Carriers should be kept behind, and submarines should be placed with the battleships.
A battleship picket line defends the fragile carriers by shooting down incoming enemy airplanes while simultaneously soaking up damage from enemy battleships and maybe sinking a few vessels on their own. The submarines placed with the battleships help by sinking enemy battleships while avoiding carriers.
If you are able to, always wait with placing your units until you can see the enemy. Also, try to keep a reserve of units that can be quickly moved to the front in order to help out in hotspots.
At Defcon 3 the exchanges start. Carriers should immediately launch fighters and bombers to strive for aerial dominance. You should also choose whether to use subs for sinking battleships or for sneaking up. When subs attack battleships they become vulnerable to enemy fire. Being able to sneak a few subs by is however no consolation if the rest of your navy lies at the bottom of the ocean. Replenish carriers with land-based fighters. Airbases regenerate fighters, carriers don't.
Each player is given 12 submarines. At 5 nukes each, they carry 60 nukes, just like all of the enemy silos combined. This makes them a great nuclear offensive weapon. Luckily for the defender, submarines are very fragile.
Submarine sweeping with carriersEdit
Carriers in anti-submarine mode are absolutely lethal against enemy subs. A single carrier can dispatch of 12 submarines, unless they are in active sonar mode. However, carriers are severely limited by their sensor range, which is comparable to the radar range of a bomber. Keep moving your sweep duty carriers around to try to root out enemy subs before they attack. When you spot surfacing submarines, put your carriers over them. If however they are outside of a reasonable range, switch to bomber launch mode. Bombers sink submarines quickly.
Submarine sweeping with bombersEdit
Bombers can be micromanaged to patrol shorelines. Bombers have long loiter time and can stay on a coastline for a good while before returning to refuel. The method is simple: launch bombers to one edge of the vulnerable coast. When they arrive there, send them to the other edge. When they reach the coastline, launch another pair of bombers to continue the patrol. Using this method of circular patrolling, bombers can quickly assault any surfacing sub and kill the majority of them before they launch a single nuke.
Submarine sweeping with submarinesEdit
Submarines in active sonar mode can find and attack enemy submarines almost as effectively as carriers can. The problem is that a submarine in active sonar advertises its position to the entire world. As such, submarines on patrol duty are easily avoided. If you do have submarines nearby when the enemy is surfacing to launch, do not hesitate to use them to eliminate the threat.
As stated before, submarines are very fragile. As such, you should support them with other naval units (mainly battleships) to protect them from incoming enemy units. It is also a good idea to move submarines in small groups of one to three units. Submarines that are dispersed are harder to attack with aerial units, and if they are revealed, you only lose one sub instead of losing the entire formation.
Subs and bombers are great units to take out enemy defences before launching a full-scale attack. However, taking out even a single silo takes a lot of effort. Systematically destroying the enemy defences one radar, airfield and silo at a time is however tremendously effective and demoralizing, and almost guarantees that the enemy will launch prematurely in order to get at least some nukes in the air.
Silos are usually placed close together. As such, the best bet to take out a silo is to concentrate on a single one and launch three to seven nukes simultaneously, depending on the distance to the silo and what the nearby defences are.
When silos launch, they are vulnerable to enemy fire. If you can provoke your enemy to go for an all-out attack, you can take out any silos with impunity using your submarines. A single hit will deplete the silo of half its remaining nukes, so even damaging all of the silos will halve the amount of ordinance coming your way. Again, target single silos at a time and try to make the missiles hit their targets simultaneously
Carriers can carry two bombers and start out with six nukes. If a bomber lands on a carrier that has no nukes left, it will not be able to reload. Move your bombers around manually to make sure that they are able to load ordinance.
Even if a carrier has no nukes left, it can still carry bombers that are already loaded. Moving your land-based bombers to carriers is a great way of extending your reach and shortening the turn-around time of bombers.