Missile roles
Tactical missiles are best for cracking a defended line or removing a small fortification cluster. Hydrogen bombs create a larger breach but require careful timing so your own advance does not stall.
MIRVs are strongest against wide economic zones because they can spread damage across cities, factories, or SAM coverage instead of hitting one point.
How to defend against nukes
SAM coverage should be layered near economic centers, missile silos, and borders that are likely to receive a breakthrough strike. One isolated battery is not enough against saturated attacks.
Do not stack all valuable buildings in one perfect-looking cluster. Spread important targets so a single blast does not remove your economy.
Warships and transports
Warships punish unsupported transports and can turn oceans into walls. Transports are useful only when protected or when the landing route is uncontested.
If the enemy controls the sea, invest in deterrence before crossing. A failed crossing is often worse than waiting.