Combat damage is dealt in two separate steps when any creature has first strike or double strike. In the first combat damage step, only creatures with first strike or double strike deal their damage. State-based actions are then checked, meaning creatures that received lethal damage are destroyed before the second combat damage step begins (CR 702.7, CR 704.5g).
In the second combat damage step, only creatures without first strike (or with double strike, who deal again) assign their damage. If the blocker was already destroyed in the first step, it is no longer on the battlefield and cannot deal its normal damage to the attacking creature (CR 509.2, CR 510.2).
It is important to note that the attacking creature must actually deal lethal damage — enough to equal or exceed the blocker's toughness — in the first strike step for this to matter. If the first strike damage is not lethal, the blocker survives into the second step and deals its damage normally (CR 704.5g).
Example: Your 2/2 first striker attacks and is blocked by your opponent's 3/3. In the first damage step, your 2/2 deals 2 damage to the 3/3 — not lethal. The 3/3 survives and deals 3 damage back in the second step, destroying your 2/2. If instead your 3/2 first striker had attacked and been blocked by a 2/2, your 3/2 deals 3 lethal first strike damage; the 2/2 dies before the second step, so your 3/2 takes no damage.
This interaction is why first strike is so powerful in combat: it grants the opportunity to eliminate blockers (or attackers) before they can deal their regular combat damage, as long as the first strike damage is lethal (CR 702.7b, CR 510.2).
Unofficial fan resource — not affiliated with or endorsed by Wizards of the Coast. Answers are AI-generated estimates grounded in the Comprehensive Rules and are not a substitute for an official judge. Verify anything match-critical.