Bolo Rising

Bolo Rising - William H. Keith Jr., Keith Laumer Humanity on the planet of Cloud has been enslaved by mechanical overlords with a penchant for harvesting body parts.

Their last line of defence, Hector, a Mark 33 Bolo had been incapacitated at the start of the invasion and now stands guard over the human slaves....

A good full length Bolo novel, with the usual ineffectual military types who mistrust the self aware giant tanks, self sacrifice and lots of action.