There was once a powerful king who wanted to take over the world with his massive 100,000 strong army.
Methodically, he disposed of enemy after enemy, all while making sure his army (through recruitment) always had exactly 100,000 men.
Finally, with only one more enemy castle to conquer, he decided to lay siege to the stronghold. The castle was small, so the king felt it was only a matter of time before it fell to his mighty army.
After the first night of the siege, the king woke up to find he had only 10,000 men left. Out in the morning fog, he saw standing atop the enemy castle, a black knight with a sword raised in victory.
Slightly disturbed at losing 90% of his army, the king decided to wait another day before attacking. He was more than confident he could take the castle with 10,000 men.
After the second night of the siege, the king woke up to find he had only 1000 men left. Again he saw standing atop the enemy castle, a black knight with a sword raised in victory.
Slightly demoralised at losing 90% of his army overnight, the king again decided to wait another day before attacking. He believed his 1000 remaining soldiers were still enough.
After the third night of the siege, the king woke up to find he had only 100 men left. Once again out in the morning fog, he saw standing atop the enemy castle, a black knight with a sword raised in victory.
Distraught at losing 90% of his army once again, the king decided to wait another day before attacking. Of his 100 men, he still had many war veterans and skilled fighters so he believed a surgical strike into the small castle could still defeat his enemy.
After the fourth night of the siege, the king woke up to find he had only 10 men left. Out in the morning fog, he saw standing atop the enemy castle, a black knight with a sword raised in victory.
Knowing victory was no longer possible, the king resigned to retreat. However to build energy for the long march home that lay ahead, he decided to retreat only after having a good nights rest.
After the fifth night of the siege, the king woke up to find he was the only one left in his army. Out in the morning fog, he saw standing atop the enemy castle, a black knight with a sword raised in victory.
The king walked to the gates of the small castle and as the gates opened, he came face to face with the black knight.
The king, finally defeated could only ask:
"Black knight, were you the one who destroyed my army every night?"
"No."