To "assert control" would mean to behave in a manner that shows authority or power to make the decision.
After Julius Caesar established control of France
For the meaning of assert as "to affirm" the opposite could be "deny."
To assert the contrary of; to oppose in words; to take issue with; to gainsay; to deny the truth of, as of a statement or a speaker; to impugn., To be contrary to; to oppose; to resist., To oppose in words; to gainsay; to deny, or assert the contrary of, something.
in which you assert
assert (boolean expression); Example: assert (a >= 0);
Because they wanted to assert Confederate control over the fort, as it was part of South Carolina.
created the federal reserve system
Demand and provide are opposite in meaning, in the sense that one is asking for something (requires its provision) and the other is supplying it.
of Control
created the federal reserve system
They founded what is now called the Federal Reserve system.
Let me assert my position for you.