out by a gigantic, deep-throated whistle. The steel doors cutting the soldiers' barracks and the arsenal into many minute compartments closed automatically. The room where the reserves and riot squad had been idling was effectively cut off from the rest of the building.
"Not that way," Winchester shouted to a prisoner who was blasting away with a flame-thrower. "Save your fire until Heim comes up with our reserves."
He stooped over and rifled the pockets of the dead Officer of the Day.
Heim came pounding up with two hundred more selected convicts, some of whom had armed themselves from the corpses of the defunct riot squad.
"It pays to have been a policeman here," Winchester said grimly, as he fingered the small mechanism he had taken from the man who lay at his feet.
"I know how those locks work. They are magnetic. You don't use keys, but set this gadget and wave it before a certain spot. Follow me closely with your men — and blast down every guard you see. Behind the third door we go through, there's enough equipment for an army."
They met with little opposition. Winchester's purge of "disloyal" police had been drastic indeed. Wholesale execution had left every post on the Moon short-handed. The two sets of sentries plus the riot squad must have represented most of the garrison. The few rebels they met in the passages went out of existence with a flicker of blue fire. It took but two minutes to reach the armory door.
"Pass out arms to everyone," ordered Winchester. "Mop up the remainder of the guards, then man the defenses of the dome and the outer walls. It won't be long before the Khan's cruisers will be coming. One of these guards must surely have sent for them.
"And," he added significantly, "if they didn't, I will!"
The convicts ran by the thousands to their stations, shouting and leaping for joy and waving their weapons in elation. At last, after years of unutterable misery and harsh treatment, they had been given a chance to win their freedom.
Throughout the dome loud speakers were bawling now as Winchester unfolded his strategy.
"We hold this fort," he told them, "and we are armed. The enemy you feared the most are now few. There are not many police left alive — and no spies! You can fight back to back and feel safe. Your neighbor will not betray you.
"The foes coming to meet us are soldiers. We can deal with them. Once they and their flat-faced overlords are out of the way, the entire Solar System is ours. We can then go to Cosmopolis and the Earth, and release our friends and kinsmen from bondage."
The rebels heard and thrilled. Some fingered their ray-guns. Others, assigned to the great siege projectors, stationed on the outer walls, manipulated the intricate mechanisms with skilled fingers.
"Stand by!" warned Winchester. "Here they come!"
Six silvery shapes had soared into the void from the distant Lunar Base. The formation split into three pairs and maneuvered for the attack. Winchester watched them tensely, his hands guiding the master control of one of the huge projectors. Heim was at another, and men as steady at the rest.
"Wait for the blink as they open their shutters to fire — then let them have it! We'll be hit, but if we fire first it will give them warning. They do not know such big guns have been mounted here."
"What a surprise they're in for!" murmured a helper nearby, patting his range dial affectionately.
Two blasts flared out almost simultaneously. Winchester saw the pair of cruisers nearest him dip, caught the flicker as they unmasked their projectors. He pressed his button.
For a long moment he sat with tightly shut eyes, unable to open them, because of the intolerable brilliance of the fierce electronic exchange.
He felt the crater rim under him shiver, heard the tumbling of thousands of tons of liquid, as portions of the wall disintegrated and fell away in glowing lava.
There were no screams of the injured. In that electric holocaust men simply ceased to exist. But Winchester could still feel and breathe, and therefore knew he was untouched.
He opened his eyes. Then he stared incredulously about him. Everything had changed. He was seated on a pinnacle of tottering masonry. For three thousand yards to the north, the outer wall was gone. To the south it was badly battered.
All the mighty projectors on that side were out of action — melted and fused. The great cables that fed them had been turned to greenish vapor by the blast. Winchester must have lost many of his best men. The cruisers had hit, and hit hard.
He turned his eyes upward and swept the sky. His scowl changed slowly to gratified amazement, and then his face spread into a smile. Overhead were two blobs of thin vapor, rapidly dissipating. To the north and south were the other four cruisers — disintegrating!
The Great Khan's main fleet was no more!
CHAPTER XXI
Force Meets Force
Again Winchester stuck his periscope up through the cleft in the glazed wreckage of the east wall. He could see the advancing Mongoloid hordes distinctly now, looking more like an army of goblins than of men. They were feeling their way across the bare Lunar plane, and dragging with them huge portable projectors.
It required hundreds of straining tractors to haul the mighty engines of destruction and their cumbersome generators. But in time the Mongoloids would reach the weakest point of the rebels' defenses — the shattered east wall.
"It won't be long now," Winchester warned over the loudspeaker system. "Be ready on the right and left, but do not open up until I order."
He settled to his vigil. The massed enemy was not yet in range. But their army already was deploying under the partial cover of several thick clumps of Lunar brush.
Winchester had been given a long breathing spell since the first battle. It had enabled him to patch up his defenses. Immediately after the destruction of the Khan's fleet, he had found a couple of televisors still working. This enabled him to do some scouting inside the Mongoloid strongholds, before they discovered his prying eye and demolished the scanners wherever they were.
The flashes Winchester had of conditions in Lunar Base, in the gutted Central Station, in Cosmopolis and elsewhere were comforting. The enemy was badly rattled, and uncertain what to do.
Since their air power was gone, except for a few small units beyond the orbit of Mars, and their police virtually nonexistent, they could not attack from above nor within. They must make a frontal assault. To do that, they had drawn to Lunar Base every soldier on the Moon, and the reserves from Earth. Now that attack was coming, but it had taken them a week to prepare.
Winchester had not been idle. He had sent scores of men as propaganda agents to all the centers of the Moon abandoned by the police. Their job was to inform the docile workers of what was taking place, prepare them for the overturn that was soon to come.
Thousands of other men had been dispatched to the now deserted Botanical Gardens, to bring up certain materials Winchester planned to use in his defense strategy. They took with them many tractor locomotives and long strings of trailers, and were escorted by a heavy body of armed men.
Heim took charge of the local repairs. He had managed to dismount some of the undamaged projectors from the west wall. They had been reset in pits in front of the ruined eastern barrier.
The last of the work was finished and the stage cleared. Winchester made a minor adjustment to his focus and looked at the enemy again. Now he saw what he had been expecting for some time. It was the black and gold-banded space yacht of Prince Lohan, gliding down out of the void above. It circled, just out of range, and settled on a spiny knob to the south of the battlefield.
Lohan had come to direct the assault in person. Winchester grunted in contentment. Let it be so. This was the final duel. It would