Rulings
If a turn has multiple combat phases, this spell can be cast during any of them as long as it's before the beginning of that phase's Declare Blockers Step.
(wotc • 2013-09-20)
Does not allow a tapped creature to block, or allow a creature to block any creatures it would not normally be able to block.
(wotc • 2004-10-04)
Rulings
If a turn has multiple combat phases, this spell can be cast during any of them as long as it's before the beginning of that phase's Declare Blockers Step.
(wotc • 2013-09-20)
Does not allow a tapped creature to block, or allow a creature to block any creatures it would not normally be able to block.
(wotc • 2004-10-04)