drive back on

drive (one) back on (something)

To force one to use some resource, especially one that had been held in reserve. It was a tough time financially, as losing my job drove me back on my savings.
See also: back, drive, on

drive someone back on something

to force someone to tap reserves of something. The hard times drove them back on their life savings. The challenges of being a corporate executive drove her back on all her personal resources.
See also: back, drive, on