1. [v]  change the order of soldiers during a march
2. [v]  march back along the same way

COUNTERMARCH is a 12 letter word that starts with C.

1. \Coun`ter*march"\ (koun`t?r-m?rch"), v. i. [imp. &
   p. p. {Countermarched} (-m?rcht"); p. pr. & vb. n.
   {Countermarching}.] (Mil.)
   To march back, or to march in reversed order.
   
         The two armies marched and countermarched, drew near
         and receded.                             --Macaulay.
   
   

2. \Coun"ter*march`\ (koun"t?r-m?rch`), n.
   1. A marching back; retrocession.
   
   2. (Mil.) An evolution by which a body of troops change front
      or reverse the direction of march while retaining the same
      men in the front rank; also, a movement by which the rear
      rank becomes the front one, either with or without
      changing the right to the left.
   
   3. A change of measures; alteration of conduct.
   
            Such countermarches and retractions as we do not
            willingly impute to wisdom.           --T. Burnet.