What is the main conflict in Of Mice and Men by John Steinbeck?

There
are many small conflicts in , but the main conflict involves the struggle
for survival, a struggle which is shared by most living things.could not survive by
himself.looks after him. So George's struggle for survival is twice as hard as it is for most
men. They nearly got killed in Weed. They ate their late three cans of beans the night before
they show up for work at the ranch. They nearly don't get the jobs they came all this way for
because they make a bad impression on the boss. He could easily tell them he didn't want them.
They make a bad impression because they arrive late, and the boss becomes suspicious of George
because he does all the talking for Lennie. But they manage to get jobs that will provide the
bare minimum for survival. They get bunks to sleep in, a roof over their heads, and food. There
is no security and they have to work long hours in the hot sun lifting 100-pound sacks of barley
onto wagons. When the barley is all harvested, chances are that they will get laid off. Why
should the owner keep providing bed and board if there is nothing for them to do? They will have
to hit the road again. And they will be competing with thousands of other homeless, desperate
men who need food and shelter.

A couple of the other characters are worse off
than George. Candy has only one hand, and he is getting old. Crooks has a broken body and the
added handicap of being black. What kind of job could he find if they laid him off at this
place? Both Candy and Crooks are living in dread of losing their jobs. There was very little
assistance available for the destitute in those days. Steinbeck made this more dramatic when he
wrote his masterpiece, . Hordes of men, women, and children came to
California hoping to find work picking fruit. The children were going hungry, and there was
nothing their parents could do for them. If they could get temporary jobs picking fruit, they
had to work hard for very little pay. And they usually had to buy food from a company store
which charged exorbitant prices.

Some of the men in Of Mice and
Men were young and strong, but they could see their futures in men like Crooks and
Candy. When they could no longer lift hundred-pound sacks and keep at it all day, they would be
summarily discharged. There were always younger men to replace them. So the conflict might be
described as one of man against man. 

A struggle for
existence naturally follows from the high rate at which all organic beings tend to increase.
There is no exception to the rule that every organic being naturally increases at so high a
rate, that if not destroyed, the earth would soon be covered by the progeny of a single
pair.
Charles Darwin, The Origin of Species 

The condition of man . . . is a condition of war of everyone against
everyone.
Thomas Hobbes