Shock and Awe

Use this Stratagem in your Shooting phase, when an ADEPTUS ASTARTES SHOCK GRENADES or LAND SPEEDER STORM unit from your army is selected to shoot. Select one enemy unit within 6" of that unit. Until the start of your next turn:
The selected unit cannot fire Overwatch or Set to Defend.
Each time a model in the selected unit makes an attack, subtract 1 from that attack's hit roll.