Discussion about Sylvan (Wood Elves).

Nah... But the Undead, where the number of units is already increasing in the middle of the battle... It forces you to act, even without spells.
P.S. - READINESS - HOT-SIT, you can't get Readiness in online play.

So, you're saying that playing defensively against the Undead is normal. That's not quite right. What will you do, wait for the opponent to use Forgetfulness, Blind, or Mind Control on you, as Major Whirlwind already explained in the previous post, or hope that your archers will be saved by the resistance of unicorns? But regardless of the unicorns' resistance, the Undead will weaken your army with Darkness while you're just sitting in defense. It's better to attack them first (it would be good to use Haste or Retribution if you have it; then, one attack against them can decide the outcome of the battle). If the Undead have a large army, the Elves have better quality and initiative. Besides, if we consider Hot-Sit, you can have time to pick up sworn enemies, which is a very good bonus.
If you're going to play defensively against some other race, then Readiness won't hurt, and it can be increased through the "Stalwart Defense" ability, and Stalwart Defense together with Readiness is just a "bulletproof vest." (This is especially helpful for Treants; they are already very resilient, and with Stalwart Defense, they become real "terminators.")