[Kromm]

1. If you are not expecting to be attacked but are, you are stunned. You still receive an active defense if you can see your attacker, but this is at -4. This most often results from tactical or social surprise.

2. If you are attacked from outside your field of vision, you get no active defense – not even if you were 100% on alert and expecting to be attacked. This most often results from an attack from behind or by someone you cannot see (invisible foe, sniper you fail a Vision roll to notice, etc.).

Notice how neither requires the other.

The -60% limitation specifically means that both conditions must apply, most often with #2 resulting from #1; e.g., the assassin not only achieves tactical surprise but also does so from behind. Requiring just one of these things would be a far less severe limitation – at worst -30%.

Both of these conditions actually have two parts, too. The first is composed of "you are surprised" and "you are stunned." The second is made up of "you can't see the attacker" and "you have no active defense." It's possible to be surprised but not stunned (say, you weren't expecting an attack but have Combat Reflexes), stunned but not surprised (you are wounded or fail a Fright Check), unable to see an attacker but able to defend (you make a Hearing roll), or unable to defend but able to see an attacker (you did an All-Out Attack). Restricting the condition to any of these smaller particles would be an even smaller limitation – at worst -20%.

Since a DF campaign will regularly feature huge monsters with vast amounts of DR and HP but very low IQ and serious mental problems, and as these will always All-Out Attack, letting the -60% version affect them with every strike would be grossly overpowered. Either charge -20% for that or don't do it at all.