Warner had taken out his little volume again and was studying it
intently. But he raised his head long enough to reply.

"I have just achieved the solution of a very important mathematical
problem," he answered in precise tones. "An army of about thirty-five
thousand men occupies a town located on a river. It is besieged by
another army of about seventy-five thousand men flushed with victory.
The besiegers occupy the river with a strong fleet. They are also led
by a general who has shown skill and extraordinary tenacity, while the
commander of the besieged has not shown much of either quality and must
feel great discouragement."

"But you're only stating the side of the besieged."

"Don't interrupt. It's impolite. I mean to be thoroughly fair. Now
come the factors favoring the besieged. The assailing army, despite its
superior numbers, is far in the enemy's country. It may be attacked at
any time by another army outside, small, but led by a very able general.
Now, you have both sides presented to you, but I have already arrived at
the determining factor. What would you say it is, Dick?"

"I don't know."

"You haven't used your reasoning powers. Remember that the man who not
merely thinks, but who thinks hard and continuously always wins. It's
very simple. The answer is in four letters, f-o-o-d, food. As we know
positively, Pemberton was able to provision Vicksburg for five or six
weeks. We can't break in and he can't break out. When his food is
exhausted, as it soon will be, he'll have to give up. The siege of
Vicksburg is over. I know everything, except the exact date."