force of circumstance
A situation over which one has little or no control and is thus forced to take certain actions. Don't tell me that you started drinking as a force of circumstance—there are plenty of other choices you could have made.
force of ˈcircumstance
a situation in which you are forced to do something by factors beyond your control: He claimed he turned to crime through force of circumstance. He hadn’t been able to find a job and his family was starving.