Comenta Richard Bejtlich en su diario:

When the attacker is allowed freedom of maneuver, the defender will lose. The side with initiative has the superior position, unless the defenses are so unsurmountable that attack is more costly than defense. Let’s return to the Famous Romans lecture for a moment. Prior to the rule of the emperor Hadrian, the Roman Empire had pursued an expansionist foreign policy. Rome had lost many battles to its neighbors, but those neighbors essentially remained on the defensive. They feared Rome would invade, conquer, and eliminate them (at worse).

When Hadrian became emperor in 117 AD, he changed Rome’s foreign policy. He decided to consolidate the empire’s borders. His most famous action was the building of Hadrian’s Wall, separating England from Scotland. The wall was the ultimate statement of defense, as is sought to keep barbarians separated from Roman cities like London.

In some respects, this ultimate defensive maneuver was a success; London flourished. However, the building of the wall signalled weakness to Rome’s enemies. Instead of being seen as a statement of strength, barbarians interpreted as a sign the Romans would not seek to conquer them. Rome looked weak, not strong. Within a century Rome would come under increasing barbarian attack, and the remaining shell of the western “empire” was formally overthrown in 476 AD.

Creo que el valor de esta anotación histórica es significativo, y estoy de acuerdo con Richard en que la defensa raras veces es la estrategia a seguir en una batalla. El enemigo que está ahí fuera dispone de los medios y recursos necesarios para hacer que la guerra dure casi eternamente, ya que no existe un desgaste físico, y el desgaste mayor de recursos técnicos, económicos o financieros suele corresponder a las fases iniciales del ataque: aprovisionamiento de medios técnicos y la elaboración de un plan de ataque.

Por último comenta:

In the final analysis, what makes you feel safer — a lack of criminals on your street, or iron bars on your windows?

Creo que no hay más que añadir.