D&D4 Wiki
Knockdown assault
fighter attack 1

Special: A character can use knockdown assault instead of the melee basic attack or bull rush part of a charge action.

Target: one creature

Attack: Strength vs. Fortitude

Hit: "Strength modifier damage, and you knock the target prone."[PHH1:MH2]

Knockdown assault is an at-will power available to fighters at 1st level.