The value of ground was to be determined by its importance to a defensive position. Where the lay of the land gave the defender a tactical advantage, by which an attacker could be defeated with the minimum of casualties to the defenders, with small-arms fire from dispersed, disguised positions and observed artillery-fire, it was to be fought for by the garrison and local reserves, which would counter-attack to regain any ground lost The changes were codified in a training manual (The Conduct of the Defensive Battle in Position Warfare) issued on 1 December 1916, which made infantry sections () rather than the battalion the basic tactical unit. Small, advanced garrisons were to repulse attacks and penetrations were to be cut off and counter-attacked immediately, without waiting for orders. Front line troops were allowed to move away from fire, preferably by advancing into no man's land but moves to the flanks and rear were also allowed.