My opponet has two units in his battlefield.
I play DE and have one Monster of the Deep and one Shades.
In the first step of his battlefield phase he decides to attack the zone with my Shades. In the Action window after i use the ability of my Monster to prevent both of his units to be chosen as attackers. So he has started an attack but no attackers.
Does his Battlefield phase end here or does it go on? Can i declare my Shades as Defenders and trigger their ability later?