It came when the tension was almost unbearable. Through his infra-red goggles, MacAloon could see a vast, dark smear, advancing inexorably, like the ominous march of a black glacier. Before the ordered ranks came the expected stampede of animals.
As if they had studied the break-through tactics of the extinct Nazis, the ‘pedes were driving huge beasts ahead of them, living tanks that were meant to smash down the mine’s fortifications. Enormous meat-eaters were thundering along on vast legs, crushing smaller carnivores in their frenzied flight. Fleet, timid vegetarians raced beside their killers, but neither thought of anything except the hideously lethal creatures close behind them.
When the animals were close to the fence, Mac snapped an order into his microphone. Instantly, flame-throwers spat at the pool of oil surrounding the mine. A fierce blaze sprang up.
The demented rabble scattered right and left—all but the meat-eaters, the biggest beasts on Venus. Too stupid to fear fire, they were the greatest danger. In idiot terror, they crashed toward the fence.
Somehow, the fishmen stood their ground. Mac knew how they felt. It was a sensation of unnerving horror to watch a gigantic animal plunging toward you, to stare at the enormous fangs in the slavering yard-wide mouth, to feel the ground trembling beneath their tremendous feet….
MacAloon opened fire. From every side of the camp, he heard answering blasts. The pounding of the machine-guns made a furious clatter. Bullets exploded savagely in the great bodies. Then horrible bellows of agony drowned every other sound.
For minutes after a man managed to pump an endless burst of slugs into a meat-eater, and saw the flesh erupt in bloody blobs, he couldn’t help shaking, though he knew the monster was already dead on its feet. Then the vast beast collapsed into the mud with a deafening splash, and he wondered if he could ever forget the terrifying sight.
When the thick, oily smoke thinned out, the smaller animals had fled into the fog. Mac sent out a squadron of fishmen, who destroyed the dying meat-eaters. If the bodies had been allowed to remain, the ‘pedes would have used them as a food supply.
The fishmen came back inside, and all the fog-wrapped world was silent. On noiseless feet, the oncoming army moved with impossible precision toward the camp.
Twenty-five defenders against uncounted millions, with only a web of wiring and a concrete wall between them and the jaws of doom. And even if they won, victory would be no more than a truce….
The six armies of centaurpedes met and fused. Narrower and narrower grew the gap between the mine and the unending wave of repulsive vermin. Then, when they were almost at the fence, the main army suddenly slowed down, and the two wings broke into double-swift march, advancing on both sides of the barrier.
“Turn on the juice!” Mac snapped into his microphone.
Abruptly, the fence began shooting off big blue sparks in the wet air. The main body of centaurpedes halted a few yards away and remained impassive. Inside, the fishmen stood frozen, staring in terror at the long, multi-legged animals, the round, intelligent-looking heads, the huge mandibles, and the upright shoulders with pairs of clever hands and arms.
Behind the camp, the encircling wings met and joined. More advanced until the surrounding army was uniform in depth. Then, with a single movement, the black cataract flooded straight at the wire fence.
“Hold your fire!” Mac yelled at his fishmen.
Around the compound, he heard Swede and Al shouting the same order. But it was too much to expect of fear-tightened native nerves. Spasmodic bursts of fire spurted out. Undaunted, the horde pressed on against the fence.
Crackling and flashing, the electrified wire suddenly flung out great streamers of sparks. The moist chitinous bodies shriveled into ashes. A stink of burned flesh polluted the heavy fog.
Apparently at an inaudible signal, the entire mass of ‘pedes fell back out of danger. MacAloon was awed. He knew that the rear of a human army, unable to see what was happening up front, would keep pushing forward. But a secret knowledge, impossible to men, made the centaurpedes act as a single entity.
Looking along the fence, Mac could see detachments of ‘pede scouts, moving warily toward the sparking barrier. While the army watched, the reconnoiterers experimentally touched the wire. A flash and they were destroyed, but not before serving their purpose. They had given the army a chance to analyze the fence’s properties.
Again the entire force moved forward, this time with more caution than before. MacAloon looked on anxiously, knowing they were aware of the danger.
“Mac!” cried Al’s voice. “What’re they going to do?”
“They’re too smart to keep electrocuting themselves,” said MacAloon tersely. “They must have a plan.”
“But what is it?”
“I don’t know,” Mac admitted.
The first ten lines halted within a foot of the flashing barricade. The next nine marched forward and mounted the backs of the first lines. Then each succeeding rank climbed those in front.
“A pyramid!” Al yapped.
The fishmen gaped up at Mac, then back at the ‘pedes. They were close to cracking.
“Wait!” Mac ordered. “Wait till boss-limpy says they’re almost to the top of the fence. Then fire low. Don’t keep firing after the pyramid falls!”
The sporadic firing ceased. Immense gaps had appeared in the pyramid, but the fence had heated red. The drain on the generators would be enormous, and this MacAloon had feared more than the few invaders that might drop across.
Swiftly, the pyramid grew until it was as high as the fence. Then, up in the lookout room, Limpy barked a signal.
Flame leaped out at the lowest line of ‘pedes, slashed back and forth. All in an instant, the pyramid collapsed. The centaurpedes retreated, leaving a ring of charred bodies around the fence. But the survivors were as numberless as ever.
In the sudden silence, agonized shrieks rang out across the compound.
“What’s wrong, Limpy?” demanded MacAloon.
“It’s Al, but I can’t see what happened!”
“Stay where you are, Swede!” Mac ordered. “Keep the fishmen fighting!”
He raced to Birchall’s station, saw that Al’s flame-thrower had jammed. Hundreds of centaurpedes had hurled themselves over the fence and surrounded two natives. Others had brought up a tree trunk and hammered a big hole in the wire. Through the gap, a full regiment was pouring into the enclosure.
“Take care of the ones inside!” Al shrieked. “I’ll stop them!”
“Don’t be a fool!” shouted Mac. “Fall back and get another flame-thrower!”
Unheeding, Al smashed a path to the fence with the butt of his weapon. ‘Pedes were already climbing up his body and wasting no time. He bit his lip and charged on. The trickle of blood running down his chin was the smallest one flowing from his torn flesh. In a last desperate lunge, he grabbed the ends of the broken fence.
“Al!” Mac cried out.
He was too late. A sheet of blue flame had sprung up. There was a piercing scream of pain beyond endurance. Then Birchall hung limply, caught, as he had intended, by the jagged ends of wire. His mangled, lifeless body, through which the current flowed, had closed the gap.
A sudden film spoiled Mac’s vision. Savagely, he blinked it away. With vicious fury, he burned down the swiftly crawling centaurpedes around him. The two fishmen, no longer surrounded, shuddered free of their fright and began to help. Under the fierce heat, all the animals in the enclosure curled and died.
Murderously calm, Mac fired a steady blast through the fence at the pyramid outside. Sizzling and frying, the formation fell to the ground.

In spite of that, the ‘pedes had won this battle. They had unleashed a new weapon while the defenders had turned to watch the struggle. A rain of vermin seemed to come from the sky. For, thrust deep into the mud outside the fence, were whip-like catapults. Ten animals were drawing back each slingshot, flinging a ‘pede into the enclosure!
Dismayed, MacAloon watched them hurtle over the wire in unbelievable numbers. Shooting wildly at them, yet fixed to the ground they were defending, the fishmen were desperately near panic.
“Stop firing!” Mac shouted.
His order was ignored. He cursed and pulled half of the natives away, giving their flame-throwers to the remaining guards. The first half he sent inside the compound with snapped instructions. The others he placed just before the concrete rampart. Armed with two weapons instead of one, each fishmen had double firing power.
“Let them reform their ranks inside the camp,” Mac ordered. “Then let them have it!”
Limpy communicated the command to Swede on the other side of the compound. The haphazard blasts stopped. Undisturbed now, the centaurpedes well into military formation, as Mac had expected. When their lines were twenty deep, they advanced, a black, tight unit with champing mandibles.
“Now!” MacAloon roared.
A withering wall of flame lashed out, burning down the invaders by the hundreds. But reinforcements kept flying over the blue-flashing fence. And under cover of the air invasion, the pyramids were being built again! The fishmen, backed up against the curved concrete barricade, were unable to reach this new threat with a stream of fire.
Obeying his previous instructions, a squad of fishmen came staggering through the doors in the wall. They dragged oxygen and hydrogen tanks that were connected in pairs by flexible, insulated hoses with triggered nozzles.
“Forward!” Mac commanded.
Limpy passed the word around the besieged mine, and fishmen advanced with blazing flame-throwers. Behind them, the reserves hauled up the tanks. Slowly, stubbornly, the tide of centaurpedes was driven back into the fence. An ear-splitting crackle, and they were gone, a smoking pile of cinders.
Even after the camp was clear, Mac did not rest. He drove the reserves to the fence and kept them firing at the enemy beyond.
“Not the ‘pedes!” he shouted. They looked up, bewildered, wondering why ammunition should be used, if not to burn down the foe. “Melt the catapults!” he ordered.
The natives understood at last that the hand-weapons were too feeble to reduce the crude plastic slingshots, but that the tank flame-throwers were not. They blasted out at the catapults.
But the centaurpedes were damnably shrewd. In half the time it had taken the fishmen to comprehend, the vermin had begun pulling up their slingshots and retreating out of range.
Harrying his forces to get the catapults, Mac glanced aside and swore viciously. In the gaps between his widely spaced crew, more pyramids were forming.
“Forget the slingshots!” he yelled. “They can wait till later!”
The revised order didn’t make sense to the fishmen. They couldn’t see that, while their attention was diverted, the main army could pour over the fence on a secure pyramid. They blasted away at the slingshots and ignored the wall of ‘pedes.
The deadly animals saw their chance and acted. With quick cunning, they sent over a torrent of invaders. Chattering in fear, the fishmen switched their attack to the pyramids, but they were too late. They were being driven back by the vermin inside the fence, and more and more were coming over.
“I can’t hold them, Mac,” came Swede’s unalarmed voice.
“I can’t either,” Mac said tensely. “Get the fishmen and fuel tanks into the compound.”
Shrill screams erupted from the natives. Faced by alert, precise ranks marching toward them, they threw down their weapons and rushed for the concrete wall.