Warlord Attack 13Denying Smite
No matter how your enemy maneuvers, something comes between it and its quarry—and that something is you.
Encounter Martial, Weapon
Standard Action Melee weapon
Target: One creature
Attack: Strength vs. AC
Hit: 3[W] + Strength modifier damage.
Effect: Choose one ally within 5 squares of you. The target cannot attack that ally with melee or ranged attacks until the end of your next turn.
Published in Player's Handbook, page(s) 149, Class Compendium.