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The supporting fortresses arranged around Sarmizegetusa created defense-in-depth that attackers had to penetrate before reaching the capital. The concentric layers meant that enemy force advancing toward center would encounter repeated resistance, each fortress delaying the advance and inflicting casualties. The cumulative effect of fighting through multiple defensive positions could exhaust attacking army before it reached primary objective.
The strategic passes that provided access to highlands were controlled by fortresses positioned to observe and block movement. The enemy attempting to advance toward Dacian heartland had to either reduce these blocking positions (costly in time and casualties) or bypass them (leaving hostile forces in rear threatening supply lines). Neither option was attractive, the dilemma being precisely what defenders intended when they positioned fortresses to create such choices.
The communication system that connected fortresses allowed rapid intelligence sharing. The beacon fires that could be seen from multiple positions transmitted simple but critical information—enemy sighted, attack underway, assistance needed, all-clear. The pre-arranged signal codes allowed more complex messages using combinations of fires, timing, and positioning. The system was not perfect—weather could make signals invisible, enemy could attempt deceptive signals—but it provided baseline communication capability that was better than isolated fortresses relying solely on messengers.
The mutual support capacity meant that fortress under attack could expect assistance from neighbors if they could hold long enough for relief to arrive. The garrison that maintained defense for days or weeks while relief force was assembled provided time for coordination that might allow defeat of besieging enemy rather than merely delaying eventual capture. The knowledge that help might arrive sustained morale during difficult sieges.
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