For example, is this scenario possible:
I have a Kuriboh: Explosive Body in the field, which reads
When this monster is knocked out in battle, deal damage equal to its defense to an opposing monster.
My opponent has two sidekicks.
I declare attackers and attack with no characters/monsters.
There are no attackers to assign blockers to so we immediately enter the actions and globals portion of the attack step.
I now use Crush Card Virus (KO one of your monsters to KO an opponent's monster up to 1 level higher), KO my Kuriboh to KO a sidekick, and have Kuriboh deal damage equal to his defense to the second sidekick.
Would something like that be possible or must you attack with at least one character/monster if you enter the attack step?