A War of Stockpiles
Iran
The first stone left its cradle before the Persian sentries had finished their morning prayers.
Alexander had ordered the firing sequence at dawn, when the light would blind anyone looking west from Darius’s encampment. Forty ballistae released in unison, their arms snapping forward with a sound like the sky cracking open. The bolts climbed in steep arcs over the narrow corridor of Thermopylae, black against the pale morning, and for three long seconds the only noise was the creak of rope and the hiss of displaced air.
Then the impacts began.
The first volley struck the forward batteries of Darius’s camp with devastating precision. Catapult frames splintered. Ammunition stores detonated into clouds of gravel and dust. Men who had been sleeping beside their engines woke only long enough to understand what was happening before a second wave arrived, sixteen seconds behind the first, calibrated to strike the positions where survivors would be scrambling to respond. Alexander’s engineers had spent weeks calculating trajectories through the pass, accounting for the way the cliff walls funneled wind. Each bolt had been assigned a target. Each target ceased to exist.
From his command platform, elevated on a wooden tower behind the third line of ballistae, Alexander watched the dust columns rise over the Persian camp. His chief engineer, Diades, stood beside him with a wax tablet, marking impacts.
“Thirty-six confirmed strikes from the first salvo,” Diades said. “Four fell short into the gorge.”
“Reload.”
“Already underway.”
Alexander permitted himself no satisfaction. The opening bombardment had been devastating, but it was also the easiest phase. Darius had not expected it. That advantage was now spent, permanently and completely, and what followed would be a different kind of arithmetic.
It took the Persians less than an hour to answer.
The sound was different from their side. Darius’s catapults were cruder, larger, designed to lob massive stones in high parabolic arcs rather than to strike with any particular accuracy. They compensated for imprecision with volume. When the Persian response came, it came as a rain: dozens of boulders tumbling through the sky at once, their shadows rippling across the limestone walls of the pass.
Alexander did not flinch. He simply nodded to Diades.
Along the Macedonian line, a second set of ballistae pivoted upward. These were different from the siege engines that had fired the opening salvo. They were smaller, lighter, mounted on rotating platforms that allowed rapid repositioning. Their operators did not aim at the Persian camp. They aimed at the sky.
The first intercept was almost beautiful. A ballista bolt caught a descending boulder at the apex of its arc and shattered it into a spray of harmless fragments that pattered down across the field like hail. Then another. Then three more in rapid succession. The Macedonian intercept crews worked with mechanical efficiency, each team tracking an incoming projectile, leading its descent, and releasing at the precise moment calculated to produce a mid-air collision.
Of the forty-one stones Darius’s catapults hurled in that first retaliatory barrage, twenty-nine were destroyed before they reached the Macedonian lines. Eight struck empty ground. Four found targets: two supply wagons, a field hospital tent, and a section of palisade wall that sheltered a contingent of Thessalian allies who had positioned their own smaller camp adjacent to Alexander’s.
The Thessalian commander, a stocky man named Parmenion, arrived at Alexander’s platform within the hour, dust in his beard and fury in his voice.
“Four of my men are dead. Twelve wounded.”
“I intercepted twenty-nine of their stones.”
“You missed twelve.”
“I missed four. Eight hit dirt.”
“The four that didn’t hit dirt hit my camp.”
Alexander absorbed this without argument. “Your camp is closest to the eastern approach. I will reposition two intercept batteries to cover your sector.”
“And if the next volley is larger?”
“Then I will need more intercept bolts.”
This was the calculation that occupied both commanders as the days wore on. The bombardments continued, sporadic and grinding. Alexander’s siege ballistae struck Darius’s camp with ruthless accuracy whenever his scouts identified a new emplacement or supply depot. Darius’s catapults answered with massive, sweeping barrages that relied on sheer quantity to overwhelm the intercept screen. Sometimes they succeeded. A bakery. A latrine trench. Twice more, the Thessalian camp, despite the repositioned batteries.
Each interception cost Alexander a precision bolt, hand-machined by Diades’s engineers from hardened ash and tipped with iron. Each one took two days to manufacture. Darius’s stones, by contrast, were stones. The gorge was full of them.
On the ninth day, Darius stood in what remained of his forward command tent, a canvas structure now perforated with holes and shored up with salvaged timber. His general, Bessus, laid out the situation.
“We have lost perhaps a third of our catapults. Crews can be replaced. Timber framing is abundant. Stones can be hewed.” Bessus gestured toward the mountains. “What we cannot replace is time. Each day, their precise strikes destroy more than our barrages destroy in return. If this continues, we will have nothing left to fire from.”
“And their interceptors?”
“They cannot shoot down everything. Each time we saturate them, some stones land. Their allies are restless. The Thessalians are already grumbling. If we can maintain volume long enough, the pressure on their coalition may do what our stones cannot.”
Darius nodded slowly and walked to the rear of the camp, where the ammunition reserves were piled. It was not an impressive sight: rough-cut boulders stacked in uneven rows, many of them little more than rubble scavenged from collapsed fortifications. But there were thousands of them, stretching back into the mouth of the gorge.
The question was whether it was enough.
Three hundred paces to the west, Alexander walked his own ammunition line. The intercept bolts were stored in oiled leather cases, stacked with the care appropriate to objects that each represented two days of a skilled engineer’s labor. Diades walked beside him, counting under his breath.
“At current rates of engagement, we have sufficient intercept capacity for four to five more weeks.”
“And the siege bolts?”
“Thirty days, if we maintain current tempo.”
“If Darius increases his rate of fire?”
Diades paused. “Three weeks. Perhaps fewer.”
Alexander said nothing. He stood at the end of the row and looked east, where, though he could not see it, he knew Darius was conducting the same survey, asking the same question, staring at his own pile and wondering the same thing.
Whose pile was bigger.