ther side of the world, were beginning to arrive.
The attack had begun.

At exactly six o'clock Joseph Dixon, standing on the surface four
miles from the entrance tunnel, gave the sign to the waiting units.

The first job was to break down Sherikov's defense screens. The
missiles had to penetrate without interference. At Dixon's signal a
fleet of thirty Security ships dived from a height of ten miles,
swooping above the mountains, directly over the underground
laboratories. Within five minutes the defense screens had been
smashed, and all the tower projectors leveled flat. Now the mountains
were virtually unprotected.

"So far so good," Dixon murmured, as he watched from his secure
position. The fleet of Security ships roared back, their work done.
Across the face of the desert the police surface cars were crawling
rapidly toward the entrance tunnel, snaking from side to side.

Meanwhile, Sherikov's counter-attack had begun to go into operation.

Guns mounted among the hills opened fire. Vast columns of flame burst
up in the path of the advancing cars. The cars hesitated and
retreated, as the plain was churned up by a howling vortex, a
thundering chaos of explosions. Here and there a car vanished in a
cloud of particles. A group of cars moving away suddenly scattered,
caught up by a giant wind that lashed across them and swept them up
into the air.

Dixon gave orders to have the cannon silenced. The police air arm
again swept overhead, a sullen roar of jets that shook the ground
below. The police ships divided expertly and hurtled down on the
cannon protecting the hills.

The cannon forgot the surface cars and lifted their snouts to meet the
attack. Again and again the airships came, rocking the mountains with
titanic blasts.

The guns became silent. Their echoing boom diminished, died away
reluctantly, as bombs took critical toll of them.

Dixon watched with satisfaction as the bombing came to an end. The
airships rose in a thick swarm, black gnats shooting up in triumph
from a dead carcass. They hurried back as emergency anti-aircraft
robot guns swung into position and saturated the sky with blazing
puffs of energy.

Dixon checked his wristwatch. The missiles were already on the way
from North America. Only a few minutes remained.

The surface cars, freed by the successful bombing, began to regroup
for a new frontal attack. Again they crawled forward, across the
burning plain, bearing down cautiously on