I'm new to the game, played the game about a month ago, every single match I played, I defeat my enemy by strategically hitting his homeland cities with navy, ballistic missiles or strategic bombers to cripple his economy and ability to deploy units before I move in to capture a defenseless enemy. The problem is I know how to do this, but it still happens to me; a surprise attack by a powerful navy that destroys all my cities literally till they almost don't exist and move into a wasteland before I can react. Is there a way I could defend effectively without being unable to attack? I think it will take more investment to defend all the cities instead meanwhile attacking more cost effective in my opinion.
I'm beginning to get bored when I lose instantly because of getting destroyed so quickly late game.

You think elite submarines fully upgraded are worth the effort as a defense against literally golded navy?

Ok, thanks a lot