=325.= Whenever a change of formation involves a break in the continuity of the leading the leader habitually moves at once to his new position, so as to resume leadership with the least practicable delay. He usually starts at the command of execution for the movement. Should he start for his new position before the command of execution he first cautions or Signals: =DISREGARD= for the information of the base. =326.= =Change of directing unit (base)=: Whenever a change of formation results in a change of the base, the base of the formation from which the movement is executed continues, in the absence of specific indication to the contrary, to be the base until the new base is indicated. In movements from line by which column is formed directly to a flank, the element of the column on the flank toward which the column is formed is the base upon which other similar elements regulate during the formation of the column as well as after the column is formed. =327.= =Changes of direction=: Any movement may be executed either from the halt or when marching, unless otherwise prescribed. If executed from the halt the command =forward= need not be prefixed to any other preparatory command that indicates a direction of march; thus, being at a halt, 1. =Column right=, 2. =MARCH=; but, 1. =Forward trot=, 2. =MARCH.= =328.= To insure certainty of prompt execution, commands (and signals) must be so given that their meaning is unmistakable. The preparatory command must be given at such an interval of time before the command of execution as will admit of the former being properly understood, and should be followed by a distinct pause that properly varies in length with the size of the body of troops that is to execute the movement. The command of execution should be given the instant the movement is to begin. =329.= All changes of direction are simply applications of the principle of leading as explained in pars. 323 and 367. (_a_) The =turn= (par. 386) and =half turn= (par. 388) are _special_ cases of the change of direction =in line= in that they involve a change of direction of _90°_ and _45°_, respectively; _as executed by the platoon and squad_, they differ further from the general case of the change of direction in that the leader follows a _specially prescribed arc_ during the turn (par. 387); in the troop and larger units, the leader in each case regulates the arc upon which he moves during the turn in accordance with the length of the front and the requirements of the special case. (_b_) For a change of direction in any column formation, the elements of the column successively change direction _on the same ground_, the change in each successive element being made in accordance with the principles that regulate the change of direction in line (_a_). In each successive element the leader (if any) and the guide move over the _same path that is followed by the leader at the head of the column_.