When people say 'just enough defense to keep the land you have', I genuinely don't understand.
I've gone literally all turrets. Maxed it out. 30%+ defense bonus from bonus points, 140% weapons.
And random people can still just Planned Strike me no problem. It makes me feel as if defense is actually impossible in this game, and the only way to excel is to just be enormously larger than your opponents.
How do players 'defend themselves' in a serious manner?
Spies and missiles. I don't buy military until it's time to grab. Most players reconsider when they see your retal could punch a few holes in their country. Military doesn't mean fluff at that point. Warfare and spy tech are best to get early. Remember when using missiles, the order should be: cruise, chems, then nukes. Cruise to weaken SDI, so always first. Nukes make opponents "stronger" in most cases by increasing spal and tech effectiveness.
You still fear being hit. 1 strike will not destroy or cripple you. You can easily rebuild, or just grab another country. You WILL be hit, in every game. That's a good reason to stock. Sitting on piles of cash or food is perfect target. It's important to maintain your cool after being grabbed. A dozen ABs or GS is not going recoup your losses and is a serious waste of turns and resources. Either retal 1:1 within 48 hours, or simply move on. I don't approve of EoSS, but for some its satisfying as a form of revenge.
Don't waste bonus points on defense. Depending on your build it is either booms or extra turns. Expenses bonus can be worth it later(-10% means a lot when you are troop heavy), building costs early. All depends on your strat.