The downfall of civilized states tends to come not from the direct assaults of foes, but from internal decay combined with the consequences of exhaustion in war.
B. H. Liddell HartThe most consistently successful commanders, when faced by an enemy in a position that was strong naturally or materially, have hardly ever tackled it in a direct way. And when, under pressure of circumstances, they have risked a direct attack, the result has commonly been to blot their record with a failure.
B. H. Liddell HartIf you find your opponent in a strong position costly to force, you should leave him a line of retreat as the quickest way of loosening his resistance. It should, equally, be a principle of policy, especially in war, to provide your opponent with a ladder by which he can climb down.
B. H. Liddell HartDirect pressure always tends to harden and consolidate the resistance of an opponent.
B. H. Liddell HartThe art of the indirect approach can only be mastered, and its full scope appreciated, by study of and reflection upon the whole history of war. But we can at least crystallize the lessons into two simple maxims- one negative, the other positive. The first is that, in face of the overwhelming evidence of history, no general is justified in launching his troops to a direct attack upon an enemy firmly in position. The second, that instead of seeking to upset the enemy's equilibrium by one's attack, it must be upset before a real attack is, or can be successfully launched
B. H. Liddell Hart