506.1 The combat phase has five steps, which proceed in order: beginning of combat, declare attackers, declare blockers, combat damage, and end of combat. The declare blockers and combat damage steps are skipped if no creatures are declared as attackers or put onto the battlefield attacking (see rule 508.8). There are two combat damage steps if any attacking or blocking creature has first strike (see rule 702.7) or double strike (see rule 702.4).
506.2 During the combat phase, the active player is the attacking player; creatures that player controls may attack. During the combat phase of a two-player game, the nonactive player is the defending player; that player, planeswalkers they control, and battles they protect may be attacked.
506.2a During the combat phase of a multiplayer game, there may be one or more defending players, depending on the variant being played and the options chosen for it. Unless all the attacking player’s opponents automatically become defending players during the combat phase, the attacking player chooses one of their opponents as a turn-based action during the beginning of combat step. (Note that the choice may be dictated by the variant being played or the options chosen for it.) That player becomes the defending player. See rule 802, “Attack Multiple Players Option,” rule 803, “Attack Left and Attack Right Options,” and rule 809, “Emperor Variant.”
506.2b In multiplayer games using the shared team turns option, the active team is the attacking team and the nonactive team is the defending team. See rule 805, “Shared Team Turns Option.”
506.3a If an effect would put a noncreature permanent onto the battlefield attacking or blocking, the permanent does enter the battlefield but it’s never considered to be an attacking or blocking permanent.
506.3b If an effect would put a creature onto the battlefield attacking under the control of any player except an attacking player, that creature does enter the battlefield, but it’s never considered to be an attacking creature.
506.3c If an effect would put a creature onto the battlefield attacking either a player not in the game or a permanent that’s no longer on the battlefield or isn’t either a planeswalker or a battle, that creature does enter the battlefield, but it’s never considered to be an attacking creature. See rule 508.4a.
506.3d If an effect puts a creature onto the battlefield attacking during the declare blockers step, combat damage step, or end of combat step, that creature enters the battlefield unblocked. See rule 508.4d.
506.3e If an effect would put a creature onto the battlefield blocking but the creature it would block isn’t attacking the entering creature’s controller, a planeswalker that player controls, or a battle that player protects, that creature does enter the battlefield, but it’s never considered to be a blocking creature.
506.3f If an effect would put a creature that’s also a battle onto the battlefield attacking or blocking, that permanent enters the battlefield but it’s never considered to be an attacking or blocking creature.
506.4 A permanent is removed from combat if it leaves the battlefield, if its controller or protector changes, if it phases out, if an effect specifically removes it from combat, if it’s a planeswalker that’s being attacked and stops being a planeswalker, if it’s a battle that’s being attacked and stops being a battle, or if it’s an attacking or blocking creature that regenerates (see rule 701.19), stops being a creature, or becomes a battle. A creature that’s removed from combat stops being an attacking, blocking, blocked, and/or unblocked creature. A planeswalker or battle that’s removed from combat stops being attacked.
506.4a Once a creature has been declared as an attacking or blocking creature, spells or abilities that would have kept that creature from attacking or blocking don’t remove the creature from combat.
506.4b Tapping or untapping a creature that’s already been declared as an attacker or blocker doesn’t remove it from combat and doesn’t prevent its combat damage.
506.4c If a creature is attacking a planeswalker or battle, removing that planeswalker or battle from combat doesn’t remove that creature from combat. It continues to be an attacking creature, although it is not attacking any player, planeswalker, or battle. It may be blocked. If it is unblocked, it will deal no combat damage.
506.4d A permanent that’s both a blocking creature and a planeswalker that’s being attacked is removed from combat if it stops being both a creature and a planeswalker. If it stops being one of those card types but continues to be the other, it continues to be either a blocking creature or a planeswalker that’s being attacked, whichever is appropriate.
506.4e A permanent that’s being attacked that is both a planeswalker and a battle is removed from combat if it stops being both a planeswalker and a battle. If it stops being a battle but is still a planeswalker, it is removed from combat only if it is not controlled by its protector. If it stops being a planeswalker but is still a battle, it is not removed from combat. It continues to be a battle that’s being attacked.
506.5 A creature attacks alone if it’s the only creature declared as an attacker during the declare attackers step. A creature is attacking alone if it’s attacking but no other creatures are. A creature blocks alone if it’s the only creature declared as a blocker during the declare blockers step. A creature is blocking alone if it’s blocking but no other creatures are.
506.6 Some abilities check to see whether or not a creature “had to attack” during a particular combat phase. A creature had to attack if one or more effects were requiring that creature to attack at the time attackers were declared in that combat. A creature did not “have to attack” if there were no such effects that required it to attack, even if there were no other legal attacks that could have been declared. (See rule 508.)
506.7 Some spells state that they may be cast “only [before/after] [a particular point in the combat phase],” in which that point may be “attackers are declared,” “blockers are declared,” “the combat damage step,” “the end of combat step,” “the combat phase,” or “combat.”
506.7a A spell that states it may be cast “only before (or after) attackers are declared” is referring to the turn-based action of declaring attackers. It may be cast only before (or after) the declare attackers step begins, regardless of whether any attackers are actually declared. (See rule 508.)
506.7b A spell that states it may be cast “only before (or after) blockers are declared” is referring to the turn-based action of declaring blockers. It may be cast only before (or after) the declare blockers step begins, regardless of whether any blockers are actually declared. (See rule 509.)
506.7c Some spells state that they may be cast only “during combat” or “during a certain player’s combat phase” in addition to the criteria described in rule 506.7. If a turn has multiple combat phases, such spells may be cast at an appropriate time during any of them.
506.7d Some spells state that they may be cast “only before (or after) [a particular point in the combat phase],” but don’t meet the additional criteria described in rule 506.7c. If a turn has multiple combat phases, such spells may be cast that turn only before (or after) the stated point of the first combat phase.
506.7e If a spell states that it may be cast “only before [a particular point in the combat phase],” but the stated point doesn’t exist within the relevant combat phase because the declare blockers step and the combat damage step are skipped (see rule 508.8), then the spell may be cast only before the declare attackers step ends. If the stated point doesn’t exist because the relevant combat phase has been skipped, then the spell may be cast only before the precombat main phase ends.
506.7f If a spell states that it may be cast “only during combat after blockers are declared,” but the declare blockers step is skipped that combat phase (see rule 508.8), then the spell may not be cast during that combat phase.
506.7g Rules 506.7 and 506.7a–f apply to abilities that state that they may be activated only at certain times with respect to combat just as they apply to spells that state that they may be cast only at certain times with respect to combat.