InvisibleStalke
Emperor
My approach to modern naval warfare got tested in a game with Portugal where I accidentally declared war on Zara when he had nukes and three vassals and was close to domination.
In that setup you need to kill the enemy before they get close to your shores - because they love to launch nukes from subs. So you need an outer defense ring of destroyers and attack subs that can see and kill enemy subs as they approach. Visibility promotions are good. You can also move them to cover more territory - patrolling back and forth they can cover a lot of sea.
For fleet to fleet battle, I've seen the AI using battlefleets of battleships protected by aircraft carriers and destroyers.
The basic rule of ship to ship combat is you will lose one ship to each undamaged defender of equal strength. So soften up fleets before you hit them with ships. Guided missiles are excellent for this. Nukes are fantastic. Bombers are great - if you can take out the fighter cover first. The collateral promotion for battleships is great - take this always.
Outside of wartime, its a good idea to have a scouting ship (any sort but caravels and subs are great) sail outside the enemy ports and seeing where the transports are being stacked. Watching this port should alert you to potential naval invasions.
As well as their main fleets, the AIs will have frigates/destroyers scattered through the world exploring. So a pillaging attack can pop up anywhere. A good defense against this is a few scattered fighters/airships plus a few scattered destroyers of your own. I don't bother defending every seafood tile - but if I hit a destroyer with a plane or two and then attack with my own destroyer I can usually kill it.
In that setup you need to kill the enemy before they get close to your shores - because they love to launch nukes from subs. So you need an outer defense ring of destroyers and attack subs that can see and kill enemy subs as they approach. Visibility promotions are good. You can also move them to cover more territory - patrolling back and forth they can cover a lot of sea.
For fleet to fleet battle, I've seen the AI using battlefleets of battleships protected by aircraft carriers and destroyers.
The basic rule of ship to ship combat is you will lose one ship to each undamaged defender of equal strength. So soften up fleets before you hit them with ships. Guided missiles are excellent for this. Nukes are fantastic. Bombers are great - if you can take out the fighter cover first. The collateral promotion for battleships is great - take this always.
Outside of wartime, its a good idea to have a scouting ship (any sort but caravels and subs are great) sail outside the enemy ports and seeing where the transports are being stacked. Watching this port should alert you to potential naval invasions.
As well as their main fleets, the AIs will have frigates/destroyers scattered through the world exploring. So a pillaging attack can pop up anywhere. A good defense against this is a few scattered fighters/airships plus a few scattered destroyers of your own. I don't bother defending every seafood tile - but if I hit a destroyer with a plane or two and then attack with my own destroyer I can usually kill it.
