The form of the third and fourth commands is determined by whether the turn is to terminate with the advance in line or with the halt. In the turn the squad is led by its leader (par. 367) through a change of direction of 90°. The leader (and, therefore, the guide) are restricted not only to this particular change of direction but also to a particular arc or path during the turn (par. 387). There is no special arm signal for the _turn_ as such; but, as the turn is a change of direction, the signal for the latter movement is applicable. The signal for the change of direction does not in itself indicate the degree of the turn, but the leader's subsequent signal forward or halt indicates when the change of direction is to cease. In the turn, as in any case of the march in line, the leader, subject to the restrictions just indicated, regulates the direction and gait of march, the guide conforms to the movements of the leader, and all the other troopers regulate their alignment and interval on the guide. The rate of march of the leader and the guide should not be so rapid as to make it impracticable for the troopers on the marching flank of the squad to preserve their alignment on the guide during the turn. The guide moves in the _trace of the leader during the turn_, as well as before and after the turn. When the turn is executed by the _marching squad_ the leader gives the command after he has begun to change direction and at the moment when the guide arrives at the _point where the leader straightened his horse in the new direction_ (par. 471). When executed from a _halt_ the second command can not be given as above indicated. The leader in that case begins to turn at the command of execution, while the guide, instead of beginning the actual turn at once, moves forward so as to move, during the turn, _in the trace of the leader_ (par. 367). In executing the turn dismounted the leader so regulates the length of step of the guide that the _trooper on the marching flank_ can keep the regular step corresponding to the gait at which the turn is made. The other troopers lengthen or shorten the step accordingly, maintaining the cadence and their alignment and interval with respect to the guide. If the turn be terminated by the commands: 3. =Forward=, 4. =MARCH=, all the troopers resume the regular step at the fourth command. =387.= In executing the turn in a _squad_ or _platoon_, the leader, followed by the guide, so turns on the arc of a circle that the pivot trooper, in _conforming to the guide's movements_, marches on the arc of a circle whose radius varies with the gait of the guide, this radius being 2 yards at a walk, 4 yards at a trot, and 6 yards at a gallop. When the turn is executed dismounted the corresponding radius, in either quick or double time, is 1 yard.