You foresee your foe’s attack a split second before it begins. When you cast this spell, a number of your allies equal to your spellcasting ability modifier (minimum of 1) + your proficiency bonus are not surprised. If you yourself were surprised, you must make a spellcasting check at the moment your reaction should be triggered. The DC equals the initiative number of the current turn. If the spellcasting check fails, you remain surprised and can't use a reaction to cast the spell until after your turn. If the check succeeds, you can take a reaction to cast the spell but you must be one of its targets.