How do the tractors operate? what role does the bank play? what power do the small farmers have against the banks and the tractors?

They are Caterpillars operated by the banks to clear the farmers off their land.

Just to add, these farmers are largely sharecroppers meaning that they don't own their own land. This was the beginning of agribusiness and tractors were able to do the work of many people. Farmers were not needed in previous numbers. THe farmers had no choice. The "cats" just simply mowed over their shacks.

I agree with Aslan, he seems smart.