A defensive position stops being useful when an enemy can move around it without entering the defenders' gun arcs. Remaining in place then lets the flanking force approach while the main weapons cannot answer. The warning is given through Empire: Total War, but the underlying lesson concerns fields of fire and the point at which fixed defences become a trap. The useful test is whether holding the ground still serves the defence once the guns can no longer cover the threat.
Notable Point · 41:26-41:42
When a flanking move makes a position untenable
A short tactical warning explains why defenders should abandon a position once an enemy moves around it and beyond the guns' field of fire.